In the ProboStat sample holder a disk sample can be suspended with suitable sealing material to form two separate gas chambers and each chamber supplied with desired gas mixture.

Using top and bottom (and maybe guard) electrodes the user then performs measurements with desired gradients over the sample. The voltage is measured by a high-impedance voltmeter, and is a measure of ionic transport numbers in the sample.

Measurements of total conductivity are easily performed during the emf-measurements by manual switching or automatic multiplexing of the electrodes, and the combination of these two methods is a powerful tool in the investigation of the electrical conductivity of a material.

These articles refer to ProboStat or other NORECS products, filtered with keywords: 'Transport number, Transport properties'  

ID=688

Conduction mechanism of donor and acceptor doped sodium niobate-based ceramics

Authors	Luting Lu, Linhao Li, Xiuzi Che, Gaoyang Zhao
Source	Ceramics International Volume: 48, Issue: 21, Pages: 32073-32080 Time of Publication: 2022
Abstract	Recently, NaNbO3 (NN) has become a hot topic of current research due to its antiferroelectric energy storage properties, which demand that the ceramics withstand large applied electric fields. The breakdown strength is dependent on conduction properties, but there is limited research on the conduction mechanisms of NN. Here we report that A-site donor-doping of Bi3+ (BixNa1-3xNbO3) and B-site acceptor-doping of Mg2+ (NaNb1-2/5yMgyO3) in NN lead to dramatic changes in the magnitude of the bulk conductivity (σb) and the conduction mechanism of NN ceramics. Undoped NN exhibits mixed conduction behavior with an oxide ion transport number (tion) of ∼0.44, and σb of ∼10−6 S/cm at 600 °C. A low level of Bi3+ doping (x = 0.06) suppresses the NN mixed conduction mechanism to electron conduction (tion ∼ 0), and the bulk conductivity increases significantly, σb > 10−4 S/cm at 600 °C. On the other hand, Mg2+ doping (y = 0.06) samples mainly change the σb, with the mixed ion/hole conduction (tion ∼ 0.43) and σb > 10−4 S/cm at 700 °C. The results show that the conductivity of NN increases and exhibits different conduction mechanisms with the doping of Bi3+ and Mg2+. Aliovalent doping is not beneficial to improving the insulation properties. Thus, this work provides theoretical guidance for the study of energy storage characteristics and the suppression of leakage behavior of high-temperature dielectric capacitors.
Keywords	NaNbO3; Conduction mechanisms; Chemical doping; Defect
Remark	https://doi.org/10.1016/j.ceramint.2022.07.146 Link

ID=676

Contact angle screening and asymmetric dual-phase CO2 separation membranes

Authors	Wen Xing, Anne Store
Source	Journal of Membrane Science Volume: 652, Pages: 120447 Time of Publication: 2022
Abstract	Dual-phase CO2 separation membrane consisting of molten carbonates confined in a solid matrix can separate CO2 at high temperatures. The contact angle of molten carbonates to different oxides that can potentially serve as membrane supports was screened between 450 and 650 °C. These oxides have different electrical transport properties, including oxide ion, mixed, and electronic conducting. The contact angles vary between 80° and 10° for different materials. Asymmetric membranes were fabricated using wettable oxide ion conductors BTM and CGO (Bi0.8Tm0.2O1.5 and Ce0.8Gd0.2O2-δ) infiltrated with molten carbonates supported by the most "non-wetting" oxide BPR (Bi0.8Pr0.2O1.5) selected in the contact angle screening. The membranes show CO2 flux in the range of 0.035–0.35 ml/min cm2 at temperatures from 500 to 650 °C. Compared to a symmetric membrane with similar total membrane thickness, the asymmetric architecture significantly reduces the effective membrane thickness and increases CO2 flux. After the CO2 flux measurements, the membrane was examined with SEM and EDS mapping, showing that the molten carbonates were mainly confined within the top membrane and sealing area without penetrating the support layer.
Remark	https://doi.org/10.1016/j.memsci.2022.120447 Link

ID=670

Detailed characterization of oxide-ion and proton transport numbers in Sr–Ti layered perovskites using an improved electromotive force method

Authors	Yutaro Yagi, Isao Kagomiya & Ken-ichi Kakimoto
Source	Journal of Materials Research Time of Publication: 2022
Abstract	Numerous Sr–Ti-based layered perovskite-structured compounds exhibit protonic conductivity. In a previous study, we found that a new Sr2Ti0.95Al0.05O4−δ (STA05) layered perovskite also shows evidence of protonic conductivity. However, Sr–Ti-based layered perovskites are also potential oxide-ion conductors. Detailed transport numbers for both protons and oxide-ions in Sr–Ti-based layered perovskites remain unclear. To solve this problem, we here propose an improved approach based on electromotive force (emf) measurements to account for the contributions of thermal emf and polarization to the total conductivity. In the first step of this study, the conditions for investigating actual emfs were evaluated using measurements of yttria-stabilized zirconia as a typical oxide-ion conductor. The optimized emf technique was subsequently used to evaluate the transport numbers of STA05, which was found to exhibit no oxide-ion transport. Thus, STA05 is concluded to be a mixed proton and electron conductor..
Remark	Link

ID=662

Unlocking bulk and surface oxygen transport properties of mixed oxide-ion and electron conducting membranes with combined oxygen permeation cell and oxygen probe method

Authors	Yongliang Zhang, Kevin Huang
Source	Journal of Membrane Science Volume: 644, Pages: 120082 Time of Publication: 2022
Abstract	Surface exchange kinetics and bulk diffusion of oxygen are of paramount importance to the activity of oxygen electrocatalysis and performance of electrochemical devices such as fuel cell, metal-air batteries, and oxygen separation membranes. Conventional approaches to obtaining these transport properties are often limited to single property under a specific non-operation related condition. Here we use a combined oxygen permeation cell and oxygen probe methodology to simultaneously attain rates of oxygen surface exchange and bulk conductivity/chemical diffusivity of three representative mixed oxide-ion and electron conductors, namely SrCo0.9Ta0.1O3-δ (SCT), La0.6Sr0.4CoO3-δ (LSC) and La0.6Sr0.4FeO3-δ (LSF), operated under a steady-state oxygen flux. The results explicitly show that SCT exhibit the highest oxide-ion conductivity/chemical diffusivity, fastest rates of surface oxygen exchange kinetics, thus promising to be the best oxygen electrocatalyst. We have also mapped out the distribution of oxygen chemical potential gradient across the membranes and applied B-transport number concept to illustrate the rate-limiting steps in the overall oxygen permeation process.
Remark	Link

ID=656

Protonic Transport Properties of Perovskite Heterostructures A Thin Film Study

Author	Erik E. P. Alsgaard
Source	Time of Publication: 2021
Remark	Master Thesis Materials Science for Energy and Nanotechnology Link

ID=654

Electrical transport in a molten-solid V2O5–ZrV2O7 composite

Authors	Linn Katinka Emhjellen, Ragnar Strandbakke and Reidar Haugsrud
Source	J. Mater. Chem. A Volume: 9, Pages: 18537-18545 Time of Publication: 2021
Abstract	Molten-solid composite oxides are candidates as oxygen transport membranes (OTMs) at intermediate temperatures (500–700 °C). Effects of the constituent phases and interphases on surface reactions and transport processes in these composites are elusive. Here we contribute fundamental insight to such materials systems, applying electrochemical impedance spectroscopy (EIS) and electromotive force (emf) measurements to investigate the electrical conductivity characteristics of a 30 mol% V2O5–ZrV2O7 composite with a eutectic melting point at ∼670 °C. When V2O5 melts and increases the V2O5 volume percolation, the electrical conductivity increases by a factor of 10 and the activation energy increases from 0.21 to ∼0.7 eV. The oxygen red-ox reaction at the surface changes from being rate limited by charge transfer processes to mass transfer processes as a consequence of fast oxygen exchange in molten V2O5 as compared to the all-solid composite. These effects coincide with the ionic transport number rising from essentially zero to ∼0.4, reflecting a significant increase in the relative oxide ion conductivity. Oxygen permeation across a 30 mol% V2O5–ZrV2O7 membrane was estimated to be in the same order as for several dual-phase membranes, but one magnitude lower than for single-phase mixed conducting membranes at intermediate temperatures.
Remark	DOI: 10.1039/D1TA03750A Link

ID=637

Effect of ball-milling on the phase formation and enhanced thermoelectric properties in zinc antimonides

Authors	Priyadarshini Balasubramaniana, Manjusha Battabyal, Arumugam Chandra Bose, Raghavan Gopalan
Source	Materials Science and Engineering: B Volume: 271, Pages: 115274 Time of Publication: 2021
Abstract	We report the phase formation mechanism and the enhanced thermoelectric properties of zinc antimonide (ZnSb) thermoelectric material. The phase pure ZnSb thermoelectric material is achieved using high-energy ball milling of Zn and Sb in a shorter span of time. The ZnSb phase formation is explained by the kinetic energy transferred to the powders during milling for the solid-state reaction between Zn and Sb to form the desired ZnSb phase. The repeatability in transport properties up to three thermal cycles corroborates the thermal stability of the processed samples. The thermoelectric figure of merit obtained at 600 K is ~ 0.76 for the processed phase pure ZnSb sample, the highest value in binary ZnSb reported so far. Our results address the ZnSb phase evolution in a shorter milling time and the enhanced thermoelectric properties of the ZnSb materials. The observations will help to scale up the processing of high-performance ZnSb thermoelectric materials.
Keywords	Zinc antimonide; Thermoelectric materials; Ball milling; Phase formation kinetics; X-ray diffraction; Figure of merit
Remark	https://doi.org/10.1016/j.mseb.2021.115274 Link

ID=631

Influence of Doping on the Transport Properties of Y1−xLnxMnO3+δ (Ln: Pr, Nd)

Author	Kacper Cichy and Konrad Swierczek
Source	Crystals Volume: 11, Pages: 510 Time of Publication: 2021
Abstract	It has been documented that the total electrical conductivity of the hexagonal rare-earth manganites Y0.95Pr0.05MnO3+δ and Y0.95Nd0.05MnO3+δ, as well as the undoped YMnO3+δ, is largely dependent on the oxygen excess δ, which increases considerably at temperatures below ca. 300 ◩C in air or O2. Improvement for samples maintaining the same P63cm crystal structure can exceed 3 orders of magnitude below 200 ◩C and is related to the amount of the intercalated oxygen. At the same time, doping with Nd3+ or Pr3+ affects the ability of the materials to incorporate O2, and therefore indirectly influences the conductivity as well. At high temperatures (700–1000 ◩C) and in different atmospheres of Ar, air, and O2, all materials are nearly oxygen-stoichiometric, showing very similar total conduction with the activation energy values of 0.8–0.9 eV. At low temperatures in Ar (δ ≈ 0), the mean ionic radius of Y1−xLnx appears to influence the electrical conductivity, with the highest values observed for the parent YMnO3. For Y0.95Pr0.05MnO3+δ oxide, showing the largest oxygen content changes, the recorded dependence of the Seebeck coefficient on the temperature in different atmospheres exhibits complex behavior, reflecting oxygen content variations, and change of the dominant charge carriers at elevated temperatures in Ar (from electronic holes to electrons). Supplementary cathodic polarization resistance studies of the Y0.95Pr0.05MnO3+δ electrode document different behavior at higher and lower temperatures in air, corresponding to the total conduction characteristics.
Remark	Link

ID=618

Mixed ionic-electronic transport in the high-entropy (Co,Cu,Mg,Ni,Zn)1-xLixO oxides

Authors	Maciej Mozdzierz, Juliusz Dabrowa, Anna Stepien, Marek Zajusz, Miroslaw Stygar, Wojciech Zajac, Marek Danielewski, Konrad Swierczek
Source	Acta Materialia Volume: 208, Pages: 116735 Time of Publication: 2021
Abstract	A series of the high-entropy (Co,Cu,Mg,Ni,Zn)1-xLixO oxides with a lithium substitution level of x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 is evaluated in terms of the crystal structure, morphology and transport properties, with thorough studies aimed at elucidation of the nature of different contributions to the total electrical conductivity. It is found that cubic Fm-3m structure is preserved in the whole investigated series, with (Co,Cu,Mg,Ni,Zn)0.8Li0.2O composition showing a high internal strain, supporting to some degree one of the so-called core effects, anticipated for the high-entropy materials. For samples with Li content x > 0.20 the strain is relaxed by formation of the oxygen vacancies. As unambiguously evidenced by DC polarization experiments and measured impedance spectroscopy data with ionically-blocking Au and reversible Li electrodes used, the previously reported in the literature transition to the lithium superionic conductivity in the Li-rich compounds, up to σi ≈ 1–10⋅10−3 Scm−1, is more complex, with emergence of the electronic conduction as well, reaching similar magnitude for (Co,Cu,Mg,Ni,Zn)0.7Li0.3O. The observed behavior upon increase of lithium concentration (x) can be explained by a qualitative change of the nature of the electronic and ionic defects present in (Co,Cu,Mg,Ni,Zn)1-xLixO series, with initial oxidation of 3d metals (mainly Co), followed by possible formation of the interstitial lithium, and final emergence of the oxygen vacancies. Furthermore, the recorded electrochemical properties of (Co,Cu,Mg,Ni,Zn)0.7Li0.3O lithium cell electrode, suggesting presence of intercalation-like behavior at the initial stages of lithiation, confirm the proposed mixed ionic-electronic conductivity.
Keywords	High-entropy oxides; Crystalline oxides; Lattice defects; Mixed conductor; Li-ion battery
Remark	https://doi.org/10.1016/j.actamat.2021.116735 Link

ID=614

Modification of Ruddlesden-Popper-type Nd2-xNi0.75Cu0.2M0.05O4±δ by the Nd-site cationic deficiency and doping with Sc, Ga or In: Crystal structure, oxygen content, transport properties and oxygen permeability

Authors	Anna Niemczyka, Anna Stepien, Kacper Cichy, Juliusz Dabrowa, Zijia Zhang, Barthomiej Gedziorowski, Kun Zheng, Hailei Zhao, Konrad Swierczek
Source	Journal of Solid State Chemistry Volume: 296, Pages: 121982 Time of Publication: 2021
Abstract	Nd2-xNi0.75Cu0.2M0.05O4±δ (x ​= ​0 and 0.1; M ​= ​Sc, Ga, and In) Ruddlesden-Popper-type oxides are obtained by a sol-gel route and characterized concerning phase composition and crystal structure. It is found that the largest In3+ cannot be effectively introduced into the structure, while Nd stoichiometric and cation-deficient Nd2-xNi0.75Cu0.2Sc0.05O4±δ and Nd2-xNi0.75Cu0.2Ga0.05O4±δ (x ​= ​0; 0.1) can be obtained as single-phase materials. Systematic characterization of the crystal structure at high temperatures, oxygen content, as well as transport properties reveals that while the Nd-site deficiency has rather negligible influence on the structure, it causes a substantial decrease of the oxygen content, which at high temperatures leads to a change of the dominant type of defects from the oxygen interstitials to the vacancies for Nd1.9Ni0.75Cu0.2Sc0.05O4±δ and Nd1.9Ni0.75Cu0.2Ga0.05O4±δ. The Nd-site deficiency also causes a decrease of the total conductivity. Importantly, all the examined materials exhibit full chemical stability in CO2 atmosphere, which together with moderate thermal expansion makes them good candidates for the oxygen transport membranes, which can be used e.g. in the air separation technologies. The selected Sc- and Ga-doped compounds evaluated as ceramic membranes show relatively high oxygen fluxes, with the highest value of 0.78 ​mL ​cm-2 min-1 at ca. 880 ​°C registered for 0.9 ​mm thick, dense Nd1.9Ni0.75Cu0.2Ga0.05O4±δ membrane.
Keywords	Ruddlesden-Popper oxides; Nonstoichiometric compounds; Crystal structure; Transport properties; Oxygen permeation membranes
Remark	Link

ID=603

From insulator to oxide-ion conductor by a synergistic effect from defect chemistry and microstructure: acceptor-doped Bi-excess sodium bismuth titanate Na0.5Bi0.51TiO3.015

Authors	Fan Yang, Julian S. Dean, Qiaodan Hu, Patrick Wu, Emilio Pradal-Velázquez, Linhao Li and Derek C. Sinclair
Source	Journal of Materials Chemistry A Issue: 47 Time of Publication: 2020
Abstract	The influence of Ti-site acceptor-doping (Mg2+, Zn2+, Sc3+, Ga3+ and Al3+) on the electrical conductivity and conduction mechanism of a nominally Bi-excess sodium bismuth titanate perovskite, Na0.5Bi0.51TiO3.015 (NB0.51T), is reported. Low levels of acceptor-type dopants can introduce appreciable levels of oxide-ion conductivity into NB0.51T, i.e., 0.5% Mg-doping for Ti4+ can enhance the bulk conductivity of NB0.51T by more than 3 orders of magnitude with the oxide-ion transport number going from <0.1 for NB0.51T to >0.9 at 600 °C. The intriguing electrical behaviour in acceptor-doped NB0.51T dielectrics is a synergistic effect based on the defect chemistry and ceramic microstructure in these materials. NB0.51T ceramics with extremely low levels of doping show an inhomogeneous microstructure with randomly distributed large grains embedded in a small grained matrix. This can be considered as a two-phase composite with large grains as a conductive phase and small grains as an insulating phase based on an empirical conductivity – grain size relationship. Variation in the fraction of the conductive, large grained phase with increasing doping levels agrees with the oxide-ion transport number. This electrical two-phase model is supported by finite element modelling. This study reveals the significance of ceramic microstructure on the electrical conduction behaviour of these materials and can provide a guideline for selecting suitable doping strategies to meet the electrical property requirements of NBT-based ceramics for different applications.
Remark	Link

ID=593

Crystal structures and proton transport properties of Sr2(Ti1-xMx)O4-δ (M = Fe, Al)

Authors	Yutaro Yagi, Isao Kagomiya, Ken-ichi Kakimoto
Source	Solid State Sciences Volume: 108, Pages: 106407 Time of Publication: 2020
Abstract	This study focuses on the effects of acceptor dopants in proton-conductive Sr2TiO4-based layered perovskites. We synthesized Sr2Ti0.9Fe0.1O4-δ (STF10) and Sr2Ti0.95Al0.05O4-δ (STA05) and evaluated the influence of ion substitution on their crystal structures, electrical conductivities, and proton transport properties. Our obtained results suggest that a redox reaction is the more favorable mechanism for the introduction of proton defects to Fe-doped samples compared with water vapor absorption, while the reverse is true for Al-doped samples. STF10 was found to exhibit a larger electrical conductivity at low temperatures than STA05. In addition, STF10 presented a proton transport number of 0.5 at 600 °C, while the corresponding value for STA05 was 0.5–0.6 at 450–600 °C. The higher proton transport number of STA05 at 450–550 °C compared to that of STF10 indicates that the Al-dopant suppressed the electronic conductivity owing to its constant valency. We therefore considered that characterization of the changes in material properties related to ion substitution can serve as a guide for material selection when developing proton-conducting solid oxide fuel cell technologies.
Remark	Link

ID=582

High Cu content LaNi1-xCuxO3-δ perovskites as candidate air electrode materials for Reversible Solid Oxide Cells

Authors	Anna Niemczyk, Kun Zheng, Kacper Cichy, Katarzyna Berent, Kathrin Küster, Ulrich Starke, Bisham Poudel, Bogdan Dabrowski, Konrad Åšwierczek
Source	International Journal of Hydrogen Energy Volume: 45, Issue: 53, Pages: 29449-29464 Time of Publication: 2020
Abstract	High Cu content perovskite-type LaNi1-xCuxO3-δ oxides are evaluated as alternative air electrode materials for Solid Oxide Cells. Auto-combustion synthesis allowed to obtain fine oxide powders up to a Cu content of x = 0.75 under ambient pressure. Investigations of the crystal structure, oxygen deficiency, chemical and thermal stability, as well as transport properties reveal satisfactory characteristics, with high total electrical conductivity and high concentration of oxygen vacancies at elevated temperatures. LaNi1-xCuxO3-δ-based electrode layers show low polarization resistance values in La0.8Sr0.2Ga0.8Mg0.2O3-δ-based symmetrical cells. The lowest values for Cu-rich compositions at 800 °C are 0.056 Ω cm−2 for LaNi 0.5Cu0.5O3-δ and 0.054 Ω cm−2 for LaNi0.25Cu0.75O3-δ with La0.2Ce0.8O3-δ buffer layer. For the reversible cell with LaNi0.5Cu0.5O3-δ air electrode, approx. 870 mW cm−2 power density output at 900 °C is obtained when fueled with wet H2, as well as over 3 A cm−2 current density at 2 V in the electrolysis mode.
Remark	Link

ID=566

Ruddlesden-Popper-type Nd2-xNi1-yCuyO4±δ layered oxides as candidate materials for MIEC-type ceramic membranes

Authors	Bartłomiej GÄ™dziorowski, Kacper Cichy, Anna Niemczyk, Anna Olszewska, Zijia Zhang, Szymon Kopeć, Kun Zheng, Mateusz Marzec, Marta Gajewska, Zhihong Du, Hailei Zhao, Konrad Åšwierczek
Source	Journal of the European Ceramic Society Volume: 40, Issue: 12, Pages: 4056-4066 Time of Publication: 2020
Abstract	Series of Nd2-xNi1-yCuyO4±δ Ruddlesden-Popper-type oxides is obtained by auto-combustion synthesis method and systematically characterized concerning phase composition, formation of solid state solution, crystal structure, oxygen content, as well as regarding transport properties and oxygen permeability when applied as mixed conducting ceramic membranes. The A-site deficiency x is discussed in terms of structural stability and its effect on the oxygen content, with ongoing modification of total electrical conductivity observed. In selected Nd2-xNi0.75Cu0.25O4±δ oxides the dominating oxygen defects at high temperatures can be changed from oxygen interstitials to vacancies by the induced A-site deficiency, which affects bulk- and surface-related transport coefficients, as it is observed in electrical conductivity relaxation studies. The optimized Nd1.9Ni0.75Cu0.25O4±δ sinters having increased ionic conductivity, as well as fine, well-sintered microstructure allow to achieve one of the higher reported oxygen fluxes for CO2-stable Ruddlesden-Popper-based ceramic membranes (e.g. 0.49 mL cm−2 min−1 at ca. 880 °C for 1.05 mm thickness).
Keywords	Ruddlesden-Popper oxides, Nonstoichiometric compounds, Crystal structure, Transport properties, Oxygen permeation membranes
Remark	https://doi.org/10.1016/j.jeurceramsoc.2020.04.054 Link

ID=554

Indium doping in SrCeO3 proton-conducting perovskites

Authors	Wojciech Skubida, Kun Zheng, Konrad Swierczek, Mateusz Michna, Lukasz Kondracki
Source	Journal of Solid State Chemistry Volume: 248, Pages: 121210 Time of Publication: 2020
Abstract	In this work we present results of studies of In3+ doping in strontium cerate, comprising structural aspects, and oxygen as well as proton conductivity. Crystal structure analysis of single-phase SrCe1-xInxO3-a (x ​= ​0.1, 0.2 and 0.3) materials in 25–900 ​°C temperature range indicates presence of strong orthorhombic distortion of the perovskite-type structure, similar as for the undoped SrCeO3. Limited sinterability of the obtained powders was mitigated by addition of 1 ​wt% of NiO, which allowed to manufacture dense sinters at 1400 ​°C. Electrochemical impedance spectroscopy measurements done in dry synthetic air show decrease of the ionic (oxygen) conductivity with the increase of In content, as well as associated increase of the activation energy. This indicates that formed oxygen vacancies are trapped in the structure. Overall, electrical conductivity for SrCe1-xInxO3-a in H2O- and D2O-containing atmospheres decreases with In content, but respective H+ and D+ transference numbers are larger for samples with higher indium doping. At 500 ​°C the highest proton and deuterium conductivity was recorded for SrCe0.9In0.1O3-a, reaching up to 0.70·10−4 ​S ​cm−1 and 0.26·10−4 ​S ​cm−1, respectively. Derived diffusion and surface exchange coefficients are 10−7-10−6 ​cm2 ​s−1 and 10−6-10−5 ​cm ​s−1, respectively in 500–700 ​°C temperature range.
Keywords	Strontium cerate, In doping, Crystal structure, Hydration, Transport properties, Proton conductivity
Remark	https://doi.org/10.1016/j.jssc.2020.121210

ID=551

A CO2-Tolerant Perovskite Oxide with High Oxide Ion and Electronic Conductivity

Authors
Source	Adv. Mater. Time of Publication: 2019
Abstract	Mixed ionic–electronic conductors (MIECs) that display high oxide ion con-ductivity (σo) and electronic conductivity (σe) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen sepa-ration membranes. Often MIECs exhibit sufficient σe but inadequate σo. It has been a long-standing challenge to develop MIECs with both high σo and stability under device operation conditions. For example, the well-known perovskite oxide Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) exhibits exceptional σo and electrocatalytic activity. The reactivity of BSCF with CO2, however, limits its use in practical applications. Here, the perovskite oxide Bi0.15Sr0.85Co0.8Fe0.2O3−δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σo among the highest for known MIECs, but also high CO2 tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO2. The combination of high oxide transport properties and CO2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications.
Remark	DOI: 10.1002/adma.201905200 Link

ID=546

Exploring the Role of Manganese on Structural, Transport, and Electrochemical Properties of NASICON-Na3Fe2–yMny(PO4)3–Cathode Materials for Na-Ion Batteries

Authors	Katarzyna Walczak, Bartłomiej Gędziorowski, Andrzej Kulka, Wojciech Zając, Magdalena Ziąbka, Rafał Idczak, Vinh Hung Tran and Janina Molenda
Source	ACS Applied Materials & Interfaces Volume: 11, Issue: 46 Time of Publication: 2019
Abstract	Given the extensive efforts focused on protecting the environment, eco-friendly cathode materials are a prerequisite for the development of Na-ion battery technology. Such materials should contain abundant and inexpensive elements. In the paper, we present NASICON-Na3Fe2–yMny(PO4)3 (y = 0, 0.1, 0.2, 0.3, and 0.4) cathode materials, which meet these requirements. Na3Fe2–yMny(PO4)3 compounds were prepared via a solid-state reaction at 600 °C, which allowed to obtain powders with submicron particles. The presence of manganese in the iron sub-lattice inhibits phase transitions, which occurs at ∼95 and ∼145 °C in Na3Fe2(PO4)3, changing the monoclinic structure to rhombohedral and affecting the structural and transport properties. The chemical stability of Na3Fe2–yMny(PO4)3 was thus higher than that of Na3Fe2(PO4)3, and it also exhibited enhanced structural, transport, and electrochemical properties. The observed correlation between the chemical composition and electrochemical properties proved the ability to precisely tune the crystal structure of NASICONs, allowing cathode materials with more desirable properties to be designed.
Keywords	Na-ion batteries, XRD, crystal structure
Remark	https://doi.org/10.1021/acsami.9b10184 Link

ID=544

Mn-rich SmBaCo0.5Mn1.5O5+δ double perovskite cathode material for SOFCs

Authors	Anna Olszewska, Yang Zhang, Zhihong Du, Mateusz Marzec, Konrad Świerczek, Hailei Zhao, Bogdan Dabrowski
Source	International Journal of Hydrogen Energy Volume: 44, Issue: 50 Time of Publication: 2019
Abstract	SmBaCo0.5Mn1.5O5+δ oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+δ series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70(1)·10−6 K−1 in 300–900 °C range, high concentration of disordered oxygen vacancies in 600–900 °C range (δ = 0.16 at 900 °C), and good transport properties with electrical conductivity reaching 33 S cm−1 at 900 °C in air. Consequently, the compound enables to manufacture catalytically-active cathode, with good electrochemical performance measured for the electrolyte-supported laboratory-scale solid oxide fuel cell with Ni-Gd1.9Ce0.1O2-δ|La0.4Ce0.6O2-δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ configuration, for which 1060 mW cm−2 power density is observed at 900 °C. Furthermore, the tested symmetrical SmBaCo0.5Mn1.5O5+δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ cell delivers 377 mW cm−2 power density at 850 °C, which is a promising result.
Keywords	Mn-rich layered perovskites; Physicochemical properties; Cathode materials; SOFC; Symmetrical SOFC
Remark	https://doi.org/10.1016/j.ijhydene.2019.08.254 Link

ID=541

Thermoelectric properties of A-site deficient La-doped SrTiO3 at 100–900 °C under reducing conditions

Authors	Sathya Prakash Singh, Nikola Kanas, Temesgen D.Desissa, Mats Johnsson, Mari-Ann Einarsrud, Truls Norby, Kjell Wiik
Source	Journal of the European Ceramic Society Volume: 40, Issue: 2, Pages: 401-407 Time of Publication: 2020
Abstract	Lanthanum doped strontium titanate is a potential n-type thermoelectric material at moderate and high temperatures. (La0.12Sr0.88)0.95TiO3 ceramics were prepared by two different routes, conventional sintering at 1500 °C and spark plasma sintering at temperatures between 925 and 1200 °C. Samples with grain size between 40 nm and 1.4 μm were prepared and characterized with respect to their thermoelectric transport properties at temperatures between 100 and 900 °C under reducing conditions (H2/H2O-buffer mixtures). The thermal conductivity was significantly reduced with decreasing grain size reaching a value of 1.3 W m−1. K−1 at 600 °C for grain size of 40 nm and porosity of 19%. Electrical conductivity increased with increasing grain size showing a maximum of 500 S cm−1 at 200 °C for a grain size of 1.4 μm. The highest figure-of-merit (zT) was measured for samples with 1.4 μm average grain size reaching 0.2 at 500 °C.
Remark	https://doi.org/10.1016/j.jeurceramsoc.2019.09.024 Link

ID=512

Versatile Application of Redox Processes for REBaCoMnO5+δ (RE: La, Pr, Nd, Sm, Gd, and Y) Oxides

Authors	Anna Olszewska, Konrad Świerczek, Wojciech Skubida, Zhihong Du, Hailei Zhao, Bogdan Dabrowski
Source	J. Phys. Chem. C Volume: 123, Issue: 1, Pages: 48-61 Time of Publication: 2019
Abstract	Belonging to the not fully explored REBaCo2-xMnxO5+δ system, a series of REBaCoMnO5+δ (RE: selected rare earth elements) oxides having perovskite-type structure is synthesized and studied in terms of their structural properties, oxygen content, stability, thermal expansion, and transport properties. Impact of RE3+ on physicochemical properties of the compounds is derived, with smaller cations causing a decrease of the unit cell volume, lowering of the total oxygen content and thermal expansion, but also suppressing electrical conductivity. It is shown that a proper chemical modification enables to successfully utilize REBaCoMnO5+δ in applications, in which redox processes associated with oxygen reduction/oxidation and transport determine the effectiveness of the working material. In particular, NdBaCoMnO5+δ (with larger Nd3+) shows good chemical stability in relation to Ce0.8Gd0.2O2−δ and La0.8Sr0.2Ga0.8Mg0.2O3-δ solid electrolytes and moderate thermal expansion, 20.04(4)·10–6 K–1 in 300–900 °C. In symmetrical configuration with La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte its cathodic polarization resistance is found to be only 0.036 Ω cm2 at 900 °C, making it an excellent candidate cathode for solid oxide fuel cells. At the same time, YBaCoMnO5+δ (with small and cheap Y3+) delivers reversible oxygen storage capacity surpassing 3.4 wt % during the oxygen partial pressure swing process between air and 5 vol % H2 in Ar at 500 °C.
Remark	Link

ID=509

Engineering Transport in Manganites by Tuning Local Nonstoichiometry in Grain Boundaries

Authors
Source	Advanced Materials Volume: 31, Issue: 4, Pages: 1805360 Time of Publication: 2019
Abstract	Interface‐dominated materials such as nanocrystalline thin films have emerged as an enthralling class of materials able to engineer functional properties of transition metal oxides widely used in energy and information technologies. In particular, it has been proven that strain‐induced defects in grain boundaries of manganites deeply impact their functional properties by boosting their oxygen mass transport while abating their electronic and magnetic order. In this work, the origin of these dramatic changes is correlated for the first time with strong modifications of the anionic and cationic composition in the vicinity of strained grain boundary regions. We are also able to alter the grain boundary composition by tuning the overall cationic content in the films, which represents a new and powerful tool, beyond the classical space charge layer effect, for engineering electronic and mass transport properties of metal oxide thin films useful for a collection of relevant solid‐state devices.
Remark	Link

ID=491

Thermoelectric Properties of (1-x)LaCoO₃.(x)La_0.95Sr_0.05CoO₃ composite

Authors	Ashutosh Kumar, Karuna Kumari, B Jayachandran, D Sivaprahasam and Ajay D Thakur
Source	Materials Research Express Time of Publication: 2018
Abstract	Thermopower in cobalt oxides has been a rich area of interest due to the existence of the different charge states along-with different spin states. In this report, we have systematically studied the structural and thermal transport properties of ($1-x$)LaCoO$_3$.($x$)La$_{0.95}$Sr$_{0.05}$CoO$_3$ composite. The Seebeck coefficient ($alpha$) values for the composite increases at high temperatures compared to the LaCoO$_3$ (LCO) and La$_{0.95}$Sr$_{0.05}$CoO$_3$ (LSCO) systems. The electrical conductivity ($sigma$) decreases with the increase in the LSCO fraction which may be attributed to the localization of charge carriers due to intersite diffusion. All the samples show increase in the value of $sigma$ with increase in temperature. The thermal conductivity ($kappa$) values decrease with the increase of LSCO content in the composite and the phonon thermal conductivity dominates over the total thermal conductivity. We observe a maximum value of figure of merit (ZT)$sim$0.06 at 640,K for $x=$0.05.
Remark	Link

ID=484

Assessment of layered La2-x(Sr,Ba)xCuO4-δ oxides as potential cathode materials for SOFCs

Authors	Anna Niemczyk, Anna Olszewska, Zhihong Du, Zijia Zhang, Konrad Świerczeka, Hailei Zhao
Source	International Journal of Hydrogen Energy Volume: 43, Issue: 32, Pages: 15492-15504 Time of Publication: 2018
Abstract	In this paper, selected layered cuprates with La2-x(Sr,Ba)xCuO4-δ formula are evaluated as candidate cathode materials for Solid Oxide Fuel Cells. Two synthesis routes, a typical solid state reaction and a sol-gel method yield well-crystallized La1.5Sr0.5CuO4-δ, La1.6Ba0.4CuO4-δ and La1.5Sr0.3Ba0.2CuO4-δ materials having tetragonal I4/mmm space group, but differing in morphology of the powder. Fine powders obtained using sol-gel route seem to be more suitable for preparation of the porous cathode layers having good adhesion on the solid electrolyte, but powders obtained after the solid state route can be also successfully utilized. Investigations of structural and transport properties, the oxygen nonstoichiometry and its change with temperature, thermal expansion, as well as chemical and thermal stability are systematically performed, to evaluate and compare basic physicochemical properties of the oxides. At room temperature the average valence state of copper is found to be in 2.2–2.35 range, indicating oxygen deficiency in all of the compounds, which further increases with temperature. The conducted high-temperature X-ray diffraction tests reveal moderate, but anisotropic thermal expansion of La2-x(Sr,Ba)xCuO4-δ, with higher expansion at temperatures above 400 °C occurring along a-axis, due to the oxygen release. However, the corresponding chemical expansion effect is small and the materials possess moderate thermal expansion in the whole studied temperature range. All compounds show relatively high electrical conductivity at the elevated temperatures, related to the Cu2+/Cu3+ charge transfer, with the highest values recorded for La1.5Sr0.5CuO4-δ. Comprehensive studies of chemical stability of the selected La1.5Sr0.5CuO4-δ material with La0.8Sr0.2Ga0.8Mg0.2O3-δ solid electrolyte revealed complex behavior, with stability being dependent apart from temperature, also on morphology of the powders. A model describing such behavior is presented. While it is possible to minimize reactivity and characterize electrochemical properties of the La1.5Sr0.5CuO4-δ-based cathode layer, usage of the buffer layer is indispensable to maintain full stability. It is shown that mutual chemical compatibility of La1.5Sr0.5CuO4-δ and commonly used La0.4Ce0.6O2-δ buffer layer material is excellent, with no reactivity even at 1000 °C for prolonged time. Laboratory-scale fuel cell with the La1.5Sr0.5CuO4-δ cathode sintered at the optimized temperature is able to deliver 0.16 W cm−2 at 800 °C while fueled with wet hydrogen.
Keywords	Layered cuprates, Cathodic polarization, Chemical stability, LSGM, Buffer layer, SOFC
Remark	https://doi.org/10.1016/j.ijhydene.2018.06.119 Link

ID=481

Electrochemical and degradation study of Sr0.6Na0.4SiO3-δ

Authors	Kapil Sood, Jyoti Kaswan, Surinder P. Singh, Truls Norby, Suddhasatwa Basu
Source	Journal of Solid State Electrochemistry Volume: 22, Issue: 10, Pages: 3009–3013 Time of Publication: 2018
Abstract	The high ionic conductivity of Na-doped SrSiO3 (SNS) is a topic of interest due to contradictory reports on its conductivity and stability by various groups. From a recent NMR study, it is proposed that Na+ is mainly responsible for ionic conductivity in an amorphous Na2Si2O5 phase present in SNS. The present study further extends to determine experimentally the ion transport number as well as material characteristics after long time annealing at 600 °C. The conductivity behavior of as-sintered and annealed nominally Sr0.6Na0.4SiO3-δ is investigated and a sharp fall (~ 2 order magnitude) of the same at 800 °C is found. An XPS study is included for comprehensive understanding of conductivity and degradation behavior of SNS material. On basis of the collective results, we propose a rational description of the conduction and material degradation of SNS.
Keywords	SrSiO3, Transport number, SOFC, Ionic conductivity, Protonic conductivity
Remark	Link

ID=480

Novel ReBaCo1.5Mn0.5O5+δ (Re: La, Pr, Nd, Sm, Gd and Y) perovskite oxide: influence of manganese doping on the crystal structure, oxygen nonstoichiometry, thermal expansion, transport properties, and application as a cathode material in solid oxide f

Authors	Anna Olszewska, Zhihong Du, Konrad Świerczek, Hailei Zhao and Bogdan Dabrowski
Source	Journal of Materials Chemistry A Issue: 6, Pages: 13271-13285 Time of Publication: 2018
Abstract	In this work, a novel series of Mn-containing ReBaCo1.5Mn0.5O5+δ (Re: selected rare earth elements) perovskite-type oxides is studied, with systematic measurements of physicochemical properties being reported. Comparison with the very well-studied, parent ReBaCo2O5+δ allows determination of the role of the introduced manganese concerning modification of the crystal structure at room temperature and its evolution at high temperatures, variation of the oxygen content, thermal stability of the materials, and total electrical conductivity, as well as thermal and chemical expansion. Generally, the presence of Mn cations does not affect the tendency for A-site cation ordering, resulting in an increased unit cell volume of the compounds, as well as causing an increase of the oxygen content. Reduced thermal expansion, together with high values of electrical conductivity and suitable thermal stability, makes the compounds containing larger Re3+ cations attractive from the point of view of application as cathode materials in solid oxide fuel cells. Chemical compatibility studies reveal the sufficient stability of the considered perovskites in relation to Ce0.8Gd0.2O2−δ solid electrolyte, while unexpected, somewhat increased reactivity towards La0.8Sr0.2Ga0.8Mg0.2O3−δ and La0.4Ce0.6O2−δ is also reported. Furthermore, the electrochemical tests of the symmetric cells show strong dependence of the polarization resistance of the electrode on the synthesis and sintering temperatures. For the selected and optimized NdBaCo1.5Mn0.5O5+δ layer employed in the electrolyte-supported (LSGM) symmetric cell with a CGO buffer layer, the cathodic polarization resistance is 0.043 Ω cm2 at 900 °C. A wet hydrogen-fuelled button-type cell with the NdBaCo1.5Mn0.5O5+δ-based cathode is also prepared, delivering the maximum power density exceeding 1.3 W cm−2 at 850 °C.
Remark	DOI: 10.1039/C8TA03479F Link

ID=466

Structural transformations, water incorporation and transport properties of tin-substituted barium indate

Authors	Kacper Cichy, Wojciech Skubid, Konrad Świerczek
Source	Journal of Solid State Chemistry Volume: 262, Pages: 58-67 Time of Publication: 2018
Abstract	Incorporation of water into tin-substituted BaIn1-xSnxO3-δ (x = 0.1–0.3) is shown to influence crystal structure at room temperature, structural transformations at high temperatures and ionic transport properties of the materials. Increasing tin content stabilizes oxygen vacancy-disordered perovskite-type phase, which together with large changes of the unit cell volume occurring during hydration and dehydration processes, result in a complex structural behavior, as documented by high-temperature X-ray diffraction and thermogravimetric studies. Impedance spectroscopy measurements at elevated temperatures (350–800 °C) revealed very high proton conductivity in BaIn.8Sn.2O3-δ, exceeding 1.1·10−3 S cm−1 at 500 °C, with high values of the transference number in wet air. At the same time, relaxation kinetics of the electrical conductivity showed a monotonous nature, which indicates negligible component of the electronic hole conductivity in the hydrated material. The oxides are extremely moisture-sensitive, which results in a significant mechanical stability problems, affecting possibility to prepare electrolyte membranes.
Keywords	Barium indate, Hydration, Structural transformations, Proton conductivity, Relaxation experiments
Remark	https://doi.org/10.1016/j.jssc.2018.03.004 Link

ID=437

Defect mechanisms in BaTiO3-BiMO3 ceramics

Authors
Source	Journal of the American Ceramic Society Time of Publication: 2018
Abstract	Often, addition of BiMO3 to BaTiO3 (BT) leads to improvement in resistivity with a simultaneous shift to n-type conduction from p-type for BT. In considering one specific BiMO3 composition, that is, Bi(Zn1/2Ti1/2)O3 (BZT), several prospective candidates for the origin of this n-type behavior in BT-BZT were studied—loss of volatile cations, oxygen vacancies, bismuth present in multiple valence states and precipitation of secondary phases. Combined x-ray and neutron diffraction, prompt gamma neutron activation analysis and electron energy loss spectroscopy suggested much higher oxygen vacancy concentration in BT-BZT ceramics (>4%) as compared to BT alone. X-ray photoelectron spectroscopy and x-ray absorption spectroscopy did not suggest the presence of bismuth in multiple valence states. At the same time, using transmission electron microscopy, some minor secondary phases were observed, whose compositions were such that they could result in effective donor doping in BT-BZT ceramics. Using experimentally determined thermodynamic parameters for BT and slopes of Kröger-Vink plots, it has been suggested that an ionic compensation mechanism is prevalent in these ceramics instead of electronic compensation. These ionic defects have an effect of shifting the conductivity minimum in the Kröger-Vink plots to higher oxygen partial pressure values in BT-BZT ceramics as compared to BT, resulting in a significantly higher resistivity values in air atmosphere and n-type behavior. This provides an important tool to tailor transport properties and defects in BT-BiMO3 ceramics, to make them better suited for dielectric or other applications.
Remark	DOI: 10.1111/jace.15403, Version of Record online: 8 JAN 2018 Link

ID=432

Microstructural engineering and use of efficient poison resistant Au-doped Ni-GDC ultrathin anodes in methane-fed solid oxide fuel cells

Authors
Source	International Journal of Hydrogen Energy Volume: 43, Issue: 2, Pages: 885–893 Time of Publication: 2018
Abstract	Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-doped-ceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 °C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au-doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H2O mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Nisingle bondAu surface alloy that inhibited carbonisation and poisoning of the active nickel surface.
Keywords	SOFC; Ultrathin film anodes; Magnetron sputtering; Gadolinia doped ceria; Carbon-tolerant; Gold doping
Remark	https://doi.org/10.1016/j.ijhydene.2017.11.020 Link

ID=430

Asymmetric tubular CaTi0.6Fe0.15Mn0.25O3-δ membranes: Membrane architecture and long-term stability

Authors	Wen Xing, Marie-Laure Fontaine, Zuoan Li, Jonathan M. Polfus, Yngve Larring, Christelle Denonville, Emmanuel Nonnet, Adam Stevenson, Partow P. Henriksen, Rune Bredesen
Source	Journal of Membrane Science Volume: 548, Pages: 372-379 Time of Publication: 2018
Abstract	Three architectures of asymmetric tubular oxygen transport membranes (OTM) based on CaTi0.6Fe0.15Mn0.25O3-δ were fabricated with various thicknesses of the tubular porous supports and the dense membrane layers. This was achieved by a two-step firing method combining water based extrusion and dip-coating. The oxygen flux of the tubular membranes was characterized as a function of temperature and oxygen partial pressure on both feed and sweep sides for the different architectures. The flux exhibits different functional dependencies with respect to the oxygen partial pressure gradient and the membrane architecture. Numerical simulations using a Dusty-gas model were conducted to evaluate the effect of the porous support microstructure and thickness on oxygen partial pressure gradient inside the porous media. Results from this work were used to establish dependency of the flux with respect to bulk transport properties of the material, surface kinetics and architecture of the porous support. Furthermore, long-term stability of the produced tubular asymmetric membrane operated in CO2-containing atmospheres was assessed over half a year. The membrane exhibited a stable oxygen flux without showing significant flux degradation.
Keywords	OTM, Asymmetric tubular membrane, Oxygen flux, CaTiO3, Long-term stability
Remark	https://doi.org/10.1016/j.memsci.2017.11.042 Link

ID=407

Suppression of electrical conductivity and switching of conduction mechanisms in ‘stoichiometric’ (Na0.5Bi0.5TiO3)1−x(BiAlO3)x (0 ≤ x ≤ 0.08) solid solutions

Authors	Fan Yang, Patrick Wu and Derek C. Sinclair
Source	Journal of Materials Chemistry C Volume: 5, Pages: 7243-7252 Time of Publication: 2017
Abstract	(Na0.5Bi0.5TiO3)1−x(BiAlO3)x (0 ≤ x ≤ 0.08) solid solutions were prepared by a solid state reaction and their electrical properties were established by ac impedance spectroscopy and electromotive force transport number measurements. Incorporation of BiAlO3 (BA) decreases the electrical conductivity of Na0.5Bi0.5TiO3 (NBT) and sequentially changes the conduction mechanism with increasing x from predominant oxide-ion conduction to mixed ionic–electronic conduction and finally to predominant electronic conduction. The suppressed oxide-ion conduction by BA incorporation significantly reduces the dielectric loss at elevated temperatures and produces excellent high-temperature dielectric materials for high BA contents. The possible reasons for the suppressed oxide-ion conduction in the NBT–BA solid solutions have been discussed and we propose that the local structure, especially trapping of oxygen vacancies by Al3+ on the B-site, plays a key role in oxide-ion conduction in these apparently ‘stoichiometric’ NBT-based solid-solution perovskite materials.
Remark	DOI: 10.1039/C7TC02519J Link

ID=405

Mixed ionic–electronic conduction in K1/2Bi1/2TiO3

Authors	Linhao Li, Ming Li, Ian M. Reaney and Derek C. Sinclair
Source	J. Mater. Chem. C Volume: 5, Pages: 6300-6310 Time of Publication: 2017
Abstract	Recently, it has been reported that the Pb-free piezoelectric perovskite Na1/2Bi1/2TiO3 (NBT) can be compositionally tuned by close control of the A-site starting stoichiometry to exhibit high levels of oxide-ion conduction. The related K1/2Bi1/2TiO3 (KBT) perovskite has also drawn considerable interest as a promising Pb-free piezoelectric material; however, its conduction properties have been less extensively investigated. Here we report on the influence of the K/Bi ratio in the starting composition on the electrical properties using a combination of impedance spectroscopy and ion-transport property measurements. KBT ceramics exhibit mixed ionic–electronic (oxide-ion) conduction with tion ∼ 0.5 at 600–800 °C and although variations in the A-site starting stoichiometry can create a ∼1 order of magnitude difference in the bulk conductivity at >500 °C, the conductivity is low (ca. 0.1 to 1 mS cm−1 at 700 °C) and the activation energy for bulk conduction remains in the range ∼1.2 to 1.5 eV. The high temperature electrical transport properties of KBT are therefore much less sensitive to the starting A-site stoichiometry as compared to NBT. However, KBT ceramics exhibit non-negligible proton conduction at lower temperatures (<300 °C). For K/Bi ≥ 1 the total conductivity of KBT ceramics at room temperature can be as high as ∼0.1 mS cm−1 under wet atmospheric conditions. This study demonstrates ionic conduction to be a common feature in A1/2Bi1/2TiO3 perovskites, where A = Na, K.
Remark	DOI: 10.1039/C7TC01786C Link

ID=390

Sm6-xMoO12-δ (x = 0, 0.5) and Sm6WO12 – Mixed electron-proton conducting materials

Authors
Source	Solid State Ionics Time of Publication: 2017
Abstract	Samarium molybdates Sm6-xMoO12-δ (x = 0, 0.5) and samarium tungstate Sm6WO12 – potential mixed electron-proton conductors have been studied by X-ray diffraction, Raman spectroscopy, SEM and impedance spectroscopy (in ambient air and in dry and wet air). Solid solutions differing in structure have been obtained in the Sm2O3-MoO3 system at 1600 °C. The samarium molybdate Sm6MoO12 has the fluorite structure (Fm¯3m). The less samarium rich solid solution Sm5.5MoO11.25 crystallizes in a rhombohedral (View the MathML sourceR3¯) structure. The morphotropic transformation is due to the change in the chemical composition of the solid solution with decreasing Sm3 + concentration. The total conductivity of the cubic fluorite phase Sm6MoO12 at 750 °C in air (1.48 × 10− 3 S/cm, Ea = 1.22 eV) is an order of magnitude higher than that of rhombohedral Sm5.5MoO11.25 (2.34 × 10− 4 S/cm, Ea = 1.11 eV). At low temperatures (T < 500 °C), the Arrhenius plot of total conductivity for Sm6MoO12 and Sm5.5MoO11.25 in air deviates from linearity, suggesting that there is a proton contribution to its conductivity at these temperatures, like in the case of the Sm5.4Zr0.6MoO12.3 zirconium-doped molybdate. Below ~ 500 °C, Sm6MoO12 fluorite and fluorite-like Sm6WO12 have identical Arrhenius plots of conductivity in ambient air. The region of dominant proton conductivity is wider for Sm6WO12 than Sm6MoO12, reaching temperatures as high as 750 °С for the former. The absolute values of total conductivity obtained for samarium tungstate and molybdate at 400 °С in wet air are virtually identical and close to 3 × 10− 6 S/cm, which suggests the conductivity of both compounds is dominated by protons at low temperatures and the proton transport numbers are similar.
Keywords	Phase transition; Fluorite; Fluorite-like phase; Proton-conducting membranes; Proton conductivity; Electron conductivity
Remark	http://dx.doi.org/10.1016/j.ssi.2017.01.020 Link

ID=389

The effect of Zr-substitution in La1‐xSrxCo0.2M0.6Zr0.2O3‐δ (M = Fe, Mn) on the crystal structure, thermal expansion and electronic transport properties

Authors
Source	Solid State Ionics Volume: 301, Pages: 53–58 Time of Publication: 2017
Abstract	The effect of Zr-substitution on the evolution of crystal structure, thermal expansion and the electronic transport properties is reported for La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ (0.1 ≤ x ≤ 1.0) and La1‐xSrxCo0.2Mn0.6Zr0.2O3-δ (x = 0.1, 0.2, 0.25, 0.3). La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ was found to be single-phase for the compositions investigated. The electrical conductivity of La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ demonstrated a maximum for x = 0.5, while the area specific resistance was shown to decrease significantly with increasing Sr-content due to an increased concentration of oxygen vacancies. No signs of oxygen vacancy ordering were observed. The area specific resistance of La0.3Sr0.7Co0.2Fe0.6Zr0.2O3‐δ at 600 °C is close to an order of magnitude lower than reported values for La0.4Sr0.6Co0.2Fe0.8O3‐δ. The series La1‐xSrxCo0.2Mn0.6Zr0.2O3‐δ was found as multiphase materials. The stability of both series is discussed with respect to the red-ox properties of the transition metals.
Keywords	Perovskite; Zr-substitution; X-ray diffraction; Electrical conductivity; Thermal expansion
Remark	http://dx.doi.org/10.1016/j.ssi.2017.01.011 Link

ID=372

Insights into the enhancement of oxygen mass transport properties of strontium-doped lanthanum manganite interface-dominated thin films

Authors
Source	Solid State Ionics Time of Publication: 2016
Abstract	Strontium-doped lanthanum manganite thin films were deposited by pulsed laser deposition on yttria-stabilized zirconia single crystals for a comprehensive electrochemical characterization of the material acting as a cathode. A physically-meaningful electrical model was employed to fit the electrochemical impedance spectroscopy results in order to extract the main oxygen mass transport parameters as a function of the temperature and oxygen partial pressure. The oxygen diffusion and surface exchange coefficients extracted from the analysis showed several orders of magnitude of enhancement with respect to the bulk values reported in the literature and an unexpectedly low dependence with the oxygen partial pressure. Different observations were combined to propose a mechanism for the enhanced incorporation of oxygen in interface-dominated thin films mainly based on the high concentration of oxygen vacancies expected in the grain boundaries.
Remark	http://dx.doi.org/10.1016/j.ssi.2016.08.009 Link

ID=366

Tailoring transport properties through nonstoichiometry in BaTiO3–BiScO3 and SrTiO3–Bi(Zn1/2Ti1/2)O3 for capacitor applications

Authors	Nitish Kumar, David P. Cann
Source	Journal of Materials Science Volume: 51, Issue: 20, Pages: 9404–9414 Time of Publication: 2016
Abstract	The ceramic perovskite solid solutions BaTiO3–BiScO3 (BT–BS) and SrTiO3–Bi(Zn1/2Ti1/2)O3 (ST–BZT) are promising candidates for high-temperature and high-energy density dielectric applications. A-site cation nonstoichiometry was introduced in these two ceramic systems to investigate their effects on the dielectric and transport properties using temperature- and oxygen partial pressure-dependent AC impedance spectroscopy. For p-type BT–BS ceramics, the addition of excess Bi led to effective donor doping along with a significant improvement in insulation properties. A similar effect was observed on introducing Ba vacancies onto the A-sublattice. However, Bi deficiency registered an opposite effect with effective acceptor doping and a deterioration in the bulk resistivity values. For n-type intrinsic ST–BZT ceramics, the addition of excess Sr onto the A-sublattice resulted in a decrease in resistivity values, as expected. Introduction of Sr vacancies or addition of excess Bi on A-site did not appear to affect the insulation properties in air. These results indicate that minor levels of nonstoichiometry can have an important impact on the material properties, and furthermore it demonstrates the difficulties encountered in trying to establish a general model for the defect chemistry of Bi-containing perovskite systems.
Remark	DOI: 10.1007/s10853-016-0186-z Link

ID=356

Controlling mixed conductivity in Na1/2Bi1/2TiO3 using A-site non-stoichiometry and Nb-donor doping

Authors	Linhao Li, Ming Li, Huairuo Zhang, Ian M. Reaney and Derek C. Sinclair
Source	J. Mater. Chem. C Volume: 4, Pages: 5779-5786 Time of Publication: 2016
Abstract	Precise control of electronic and/or ionic conductivity in electroceramics is crucial to achieve the desired functional properties as well as to improve manufacturing practices. We recently reported the conventional piezoelectric material Na1/2Bi1/2TiO3 (NBT) can be tuned into a novel oxide-ion conductor with an oxide-ion transport number (tion) > 0.9 by creating bismuth and oxygen vacancies. A small Bi-excess in the nominal starting composition (Na0.50Bi0.50+xTiO3+3x/2, x = 0.01) or Nb-donor doping (Na0.50Bi0.50Ti1−yNbyO3+y/2, 0.005 ≤ y ≤ 0.030) can reduce significantly the electrical conductivity to create dielectric behaviour by filling oxygen vacancies and suppressing oxide ion conduction (tion ≤ 0.10). Here we show a further increase in the starting Bi-excess content (0.02 ≤ x ≤ 0.10) reintroduces significant levels of oxide-ion conductivity and increases tion ∼ 0.4–0.6 to create mixed ionic/electronic behaviour. The switch from insulating to mixed conducting behaviour for x > 0.01 is linked to the presence of Bi-rich secondary phases and we discuss possible explanations for this effect. Mixed conducting behaviour with tion ∼ 0.5–0.6 can also be achieved with lower levels of Nb-doping (y ∼ 0.003) due to incomplete filling of oxygen vacancies without the presence of secondary phases. NBT can now be compositionally tailored to exhibit three types of electrical behaviour; Type I (oxide-ion conductor); Type II (mixed ionic-electronic conductor); Type III (insulator) and these results reveal an approach to fine-tune tion in NBT from near unity to zero. In addition to developing new oxide-ion and now mixed ionic/electronic NBT-based conductors, this flexibility in control of oxygen vacancies allows fine-tuning of both the dielectric/piezoelectric properties and design manufacturing practices for NBT-based multilayer piezoelectric devices.
Remark	DOI: 10.1039/C6TC01719C Link

ID=335

Experimental and molecular dynamics study of thermo-physical and transport properties of ThO2-5wt.%CeO2 mixed oxides

Authors	P.S. Somayajulu, P.S. Ghosh, J. Banerjee, K.L.N.C. Babu, K.M. Danny, B.P. Mandal, T. Mahata, P. Sengupta, S.K. Sali, A. Arya
Source	Journal of Nuclear Materials Volume: 467, Issue: 2, Pages: 644–659 Time of Publication: 2015
Abstract	We have determined the thermo-physical (elastic modulus, specific heat, thermal expansion and thermal conductivity) and transport (ionic conductivity) properties of ThO2-5wt.%CeO2 mixed oxide (MOX) using a combined experimental and theoretical methodology. The specific heat, ionic conductivity and elastic properties of ThO2-5wt.%CeO2 pellets prepared by conventional powder metallurgy (POP) and coated agglomerate pelletization (CAP) routes (sintered in both air and Ar-8%H2 atmosphere) are compared with respect to homogeneity (CeO2 distribution in ThO2 matrix), microstructure, porosity and oxygen to metal ratio. The effects of inhomogeneity and pore distribution on thermal expansion and thermal conductivity of the mixed-oxide pellets are identified. Molecular dynamics (MD) simulations using the Coulomb-Buckingham-Morse-many-body model based interatomic potentials are used to predict elastic properties in the temperature range between 300 and 2000 K and thermodynamic properties, viz., enthalpy increment and specific heats of ThO2. Finally, the thermal expansion coefficient and thermal conductivity of ThO2 and (Th,Ce)O2 mixed-oxides obtained from MD are compared with available experimental results.
Keywords	ThO2-5%CeO2 MOX; Specific heat; Ionic conductivity; Temperature dependent elastic properties; Molecular dynamics simulation
Remark	doi:10.1016/j.jnucmat.2015.10.053 Link

ID=320

Protons in piezoelectric langatate; La3Ga5.5Ta0.5O14

Authors
Source	Solid State Ionics Volume: 278, Pages: 275–280 Time of Publication: 2015
Abstract	This contribution reports the hydration and electrical transport properties of effectively acceptor doped single crystalline and polycrystalline langatate, La3Ga5.5Ta0.5O14. The electrical properties are investigated over wide ranges of pH2OpH2O, pD2OpD2O and pO2pO2 in the temperature range 400 to 1000 °C. Acceptor doped langatate is dominated by oxygen vacancies in dry atmospheres and at high temperatures, and by protonic defects in wet atmospheres and at lower temperatures. The corresponding standard hydration enthalpy and entropy are − 90 ± 5 kJ/mol and − 130 ± 5 J/mol K, respectively. Further, all compositions display pure proton conductivity in wet atmospheres below 700 °C with a proton mobility enthalpy in the range of 70–75 kJ/mol, depending on doping level and crystallographic direction. Hence, protons are important for the physiochemical properties of langatate even at 1000 °C, and could therefore influence the behavior of langatate-based resonator devices. The proton conductivity is slightly anisotropic, being higher in the X- and Y- than in the Z-direction. At high temperatures and under dry conditions, electron holes and oxide ions dominate the conductivity, and the enthalpy of mobility of vacancies is 140 ± 5 kJ/mol.
Keywords	Langatate; Piezoelectric; Defects; Protons; Conductivity
Remark	doi:10.1016/j.ssi.2015.06.024 Link

ID=319

Tetragonal tungsten bronzes Nb8−xW9+xO47−δ: optimization strategies and transport properties of a new n-type thermoelectric oxide

Authors	Christophe P. Heinrich, Matthias Schrade, Giacomo Cerretti, Ingo Lieberwirth, Patrick Leidich, Andreas Schmitz, Harald Fjeld, Eckhard Mueller, Terje G. Finstad, Truls Norby and Wolfgang Tremel
Source	Materials Horizons Issue: 5, Pages: 519-527 Time of Publication: 2015
Abstract	Engineering of nanoscaled structures may help controlling the electrical and thermal transport in solids, in particular for thermoelectric applications that require the combination of low thermal conductivity and low electrical resistivity. The tetragonal tungsten bronzes Nb8−xW9+xO47 (TTB) allow a continuous variation of the charge carrier concentration while fulfilling at the same time the concept of a “phonon-glass electron-crystal” through a layered nanostructure defined by intrinsic crystallographic shear planes. The thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47−δ (0 < x < 2) were studied in the temperature range from 373 to 973 K. Structural defects and the thermal stability under various oxygen partial pressure pO2 were investigated by means of thermogravimetry, HR-TEM, and XRD. Nb8W9O47−δ was found stable at 973 K and a pO2 of ≈10−15 atm. The oxygen nonstoichiometry δ can reach up to 0.3, depending on the applied atmosphere. By increasing the substitution level x, the electrical resistivity ρ and the Seebeck coefficient S decreased. For x = 2, ρ reached 20 mΩ cm at 973 K, combined with a Seebeck coefficient of approximately −120 μV K−1. The thermal conductivity was low for all samples, ranging from 1.6 to 2.0 W K−1 m−1, attributed to the complex crystal structure. The best thermoelectric figure of merit zT of the investigated samples was 0.043, obtained for x = 2 at 973 K, but it is expected to increase significantly upon a further increase of x. The control of the oxygen non-stoichiometry δ opens a second independent optimization strategy for tetragonal tungsten bronzes.
Remark	DOI: 10.1039/C5MH00033E Link

ID=308

Proton transport properties of the RE3Ga5MO14 (RE = La, Nd and M = Si, Ti, Sn) langasite family of oxides

Authors
Source	Solid State Ionics Volume: 275, Pages: 29–34 Time of Publication: 2015
Abstract	Hydration and proton transport properties of novel, intrinsically acceptor doped compositions within the RE3Ga5MO14 family of oxides have been addressed by means of measurements of the electrical conductivity. Oxygen vacancies and protons charge compensate the acceptor in dry and wet atmospheres, respectively, and all compositions display significant proton conductivity below 1000 °C. The hydration thermodynamics is affected by M-ion substitution, and becomes more favorable in the order Si < Ti < Sn. The enthalpy of proton mobility is also strongly dependent on the M-ion; M = Si, Ti and Sn exhibit enthalpies of proton mobility of 76 ± 3, 61 ± 1 and 80 ± 2 kJ mol− 1, respectively.
Keywords	Langasites; Conductivity; Defects; Acceptor; Hydration; Protons
Remark	doi:10.1016/j.ssi.2015.03.014 Link

ID=301

Steam-promoted CO2 flux in dual-phase CO2 separation membranes

Authors	Wen Xing, Thijs Peters, Marie-Laure Fontaine, Anna Evans, Partow Pakdel Henriksen, Truls Norby, Rune Bredesen
Source	Journal of Membrane Science Volume: 482, Pages: 115–119 Time of Publication: 2015
Abstract	Steam dissolving into molten carbonates through the formation of hydroxide ions could contribute to the permeation of CO2 in dual-phase membranes under certain conditions. In this work, ceria (CeO2) supported dual-phase membranes was fabricated and the effect of steam on the transport properties has been investigated by means of flux measurements. The results show an approximate 30% increase of the CO2 flux when 2.5% steam is introduced to the feed side, while an approximate 250–300% increase of the CO2 flux is observed when introducing the same amount of steam to the sweep side. These phenomena and transport mechanisms are explained by the theory of ambipolar permeation of CO2 via various combinations of charged species.
Keywords	Dual-phase; CO2 separation membrane; Steam; Flux
Remark	doi:10.1016/j.memsci.2015.02.029 Link

ID=291

Hydrogen permeation, water splitting and hydration kinetics in Nd5.4Mo0.3W0.7O12−δ

Authors
Source	Journal of Membrane Science Volume: 476, Pages: 105–111 Time of Publication: 2015
Abstract	To investigate transport properties of Mo-substituted Nd5.4Mo0.3W0.7O12−δ for hydrogen separation application, hydrogen fluxes of Nd5.4Mo0.3W0.7O12−δ have been measured in both dry and wet sweep gases. The fluxes in dry sweep gas show lower temperature dependence at high temperatures than at low temperatures. Comparing the hydrogen permeability among rare earth tungstates, it has been revealed that the larger the RE-site cation radius, the higher the hydrogen permeation. Water splitting effect for the wet sweep gas has been confirmed by mass spectrometry. Oxygen surface kinetics under oxidizing conditions has been studied by ToF-SIMS measurements, and is significantly faster under wet conditions than dry. Hydration kinetics has been studied by conductivity relaxation measurements under reducing conditions for the first time, showing a two-fold non-monotonic behavior.
Keywords	Hydrogen permeation; Hydration kinetics; Water splitting; Oxygen surface kinetics; Nd5.4Mo0.3W0.7O12−δ
Remark	doi:10.1016/j.memsci.2014.11.013 Link

ID=268

Oxygen interstitial and vacancy conduction in symmetric Ln2 ± x Zr2 ± x O7 ± x/2 (Ln = Nd, Sm) solid solutions

Authors	A. V. Shlyakhtina, D. A. Belov, A. V. Knotko, I. V. Kolbanev, A. N. Streletskii, O. K. Karyagina, L. G. Shcherbakova
Source	Inorganic Materials Volume: 50, Issue: 10, Pages: 1035-1049 Time of Publication: 2014
Abstract	We have compared (Ln2 − x Zr x )Zr2O7 + x/2 (Ln = Nd, Sm) pyrochlore-like solid solutions with interstitial oxide ion conduction and Ln2(Zr2 − x Ln x )O7 − δ (Ln = Nd, Sm) pyrochlore-like solid solutions with vacancy-mediated oxide ion conduction in the symmetric systems Nd2O3-ZrO2 (NdZrO) and Sm2O3-ZrO2 (SmZrO). We have studied their structure, microstructure, and transport properties and determined the excess oxygen content of the (Sm2 − x Zr x )Zr2O7 + x/2 (x = 0.2) material using thermal analysis and mass spectrometry in a reducing atmosphere (H2/Ar-He). The Ln2 ± x Zr2 ± x O7 ± x/2 (Ln = Nd, Sm) solid solutions have almost identical maximum oxygen vacancy and interstitial conductivities: (3–4) × 10−3 S/cm at 750°C. The lower oxygen vacancy conductivity of the Ln2(Zr2 − x Ln x )O7 − δ (Ln = Nd, Sm; 0 < x ≤ 0.3) solid solutions is due to the sharp decrease in it as a result of defect association processes, whereas the interstitial oxide ion conductivity of the (Ln2 − x Zr x )Zr2O7 + x/2 (Ln = Nd, Sm; 0.2 ≤ x < 0.48) pyrochlore-like solid solutions is essentially constant in a broad range of Ln2O3 concentrations.
Remark	Link

ID=255

Oxide ion transport in (Nd2−xZrx)Zr2O7+δ electrolytes by an interstitial mechanism

Authors	A.V. Shlyakhtina, D.A. Belov, A.V. Knotko, M. Avdeev, I.V. Kolbanev, G.A. Vorobieva, O.K. Karyagina, L.G. Shcherbakova
Source	Journal of Alloys and Compounds Volume: 603, Issue: 5, Pages: 274–281 Time of Publication: 2014
Abstract	We have studied the structure and transport properties of ten (Nd2−xZrx)Zr2O7+x/2 (x = 0–1.27) solid solutions, which lie in the ZrO2–Nd2Zr2O7 isomorphous miscibility range. Major attention has been focused on the pyrochlore-like (Nd2−xZrx)Zr2O7+x/2 solid solutions with x = 0–0.78, which are thought to be potential interstitial oxide ion conductors. The X-ray and neutron diffraction results demonstrate that the (Nd2−xZrx)Zr2O7+x/2 (x = 0–1.27) solid solutions undergo an order–disorder (pyrochlore–defect fluorite) structural phase transition. The (Nd2−xZrx)Zr2O7+x/2 (x = 0.2–0.78) have the bulk conductivity, ∼(1.2–4) × 10–3 S/cm at 750 °C, which is two orders of magnitude higher than that of the ordered pyrochlore Nd2Zr2O7. An attempt has been made to determine the interstitial oxygen content of (Nd2−xZrx)Zr2O7+x/2 (x = 0.2; 0.67) in a reducing atmosphere using thermogravimetry and mass spectrometry. It has been shown that no reduction occurs in the NdZrO system, where neodymium has only one oxidation state, 3+.
Keywords	Fuel cells; Ionic conduction; Electrochemical impedance spectroscopy; Neutron diffraction; X-ray diffraction; SEM
Remark	http://dx.doi.org/10.1016/j.jallcom.2014.03.068 Link

ID=251

Structure and transport properties in un-doped and acceptor-doped gadolinium tungstates

Authors	Wen Xing, Protima Rauwel, Charles H. Hervoches, Zuoan Li, Reidar Haugsrud
Source	Solid State Ionics Volume: 261, Pages: 87-94 Time of Publication: 2014
Abstract	Nominal Gd6WO12, Gd5.94Ca0.06WO12 − δ, Gd5.7Ca0.3WO12 − δ and Gd5.7WO12 − δ were synthesized by solid state reaction and wet chemistry methods. The structure and morphology of the materials were analyzed by XRD, SEM and TEM and the electrical conductivity was measured as a function of temperature in reducing and oxidizing atmospheres under wet and dry conditions. The total conductivity is essentially independent of composition above 700 °C. Below 700 °C, the conductivity of Ca-doped samples is higher than that of Gd6WO12 and Gd5.7WO12 − δ and increases with increasing doping concentration. The conductivity below 700 °C is also higher under wet compared to dry conditions and, moreover, the H–D isotope effect on the conductivity is significant. Based on this, and on conductivity characterization as a function of pO2pO2 and pH2OpH2O, it was concluded that the materials are mixed ionic and electronic conductors where electrons and holes dominate at high temperatures and intermediate temperatures under sufficiently reducing and oxidizing conditions, respectively. Protons are the predominating ionic charge carriers below approximately 700 °C. The hydrogen flux through Gd5.7Ca0.3WO12 − δ was measured as a function of temperature under wet and dry sweep gas conditions, as well as with varying pH2pH2 on the feed side, confirming the picture outlined by the conductivity measurements. A defect chemical model has been derived to which the conductivity data were fitted yielding thermodynamic and transport parameters describing the functional characteristics of the materials.
Keywords	Proton; Structure; Gd6WO12; Ambipolar conductivity; Hydrogen flux
Remark	Link

ID=244

Interstitial oxide ion conduction in (Sm2 − xZrx)Zr2O7 + δ

Authors	A.V. Shlyakhtina, D.A. Belov, A.V. Knotko, I.V. Kolbanev, A.N. Streletskii
Source	Solid State Ionics Time of Publication: 2014
Abstract	The crystal structure and transport properties of (Sm2 − xZrx)Zr2O7 + x/2 (x = 0; 0.2; 0.32; 0.39; 0.48; 0.67; 0.78; 0.96; 1.14; 1.27) solid solutions have been investigated by X-ray techniques and impedance spectroscopy, respectively. The excess oxygen content of the composition with x = 0.2 has been determined by thermal analysis and mass spectrometry in a reducing atmosphere. The SmZrO system includes a two-phase (fluorite + pyrochlore) region for the (Sm2 − xZrx)Zr2O7 + x/2 (0.48 ≤ x < 0.96) solid solutions. The interstitial oxide ion conductivity of the (Sm2 − xZrx)Zr2O7 + x/2 (0.2 ≤ x < 0.48), 3 × 10− 3 S/cm at 750 °C, is comparable to the vacancy-mediated conductivity of undoped Sm2Zr2O7. The bulk conductivity of the interstitial oxide ion conductors (Sm2 − xZrx)Zr2O7 + x/2 (0.2 ≤ x < 0.48) was shown to vary little in a wide range of Sm2O3 concentrations in contrast to the vacancy mediated oxide ion conductors Sm2(Zr2 − xSmx)O7 − δ (0 ≤ x < 0.29).
Remark	Available online 2 February 2014; http://dx.doi.org/10.1016/j.ssi.2014.01.028 Link

ID=212

Defects and Transport Properties in TiNb2O7

Authors	Wen Xing, Liv-Elisif Kalland, Zuoan Li, Reidar Haugsrud
Source	Journal of the American Ceramic Society Time of Publication: 2013
Abstract	The electrical conductivity of TiNb2O7 was characterized as a function of temperature, inline image and inline image. The total conductivity was independent of inline image in the low oxygen partial pressure regime, while a dependency of inline image was observed at higher oxygen partial pressures. The conductivity increased with increasing inline image under oxidizing conditions below 700°C. Mixed electronic and protonic conduction was indicated by H/D isotope exchange and transport number measurements. A defect model based on interstitial type of hydration was established and fitted to the conductivity data allowing for determination of physicochemical parameters of hydration and electron migration.
Remark	Article first published online. DOI: 10.1111/jace.12558 Link

ID=211

CO2 removal at high temperature from multi-component gas stream using porous ceramic membranes infiltrated with molten carbonates

Authors	M.-L. Fontaine, T.A. Peters, M.T.P. McCann, I. Kumakiri, R. Bredesen
Source	Energy Procedia Volume: 37, Pages: 941–951 Time of Publication: 2013-09
Abstract	This work reports on the investigation of CO2 selective membranes for pre-combustion and post- combustion processes, in which CO2 is extracted from multi-component gas streams at intermediate temperature (400 – 600 °C). The dual-phase membranes developed in this work are designed as a porous oxide ion conducting ceramic matrix, which is infiltrated with a molten carbonate phase. Both ex-situ and in-situ characterization methods were used to study disk shaped and tubular membranes. The gas transport properties of disk-shaped membranes were further investigated under various operating conditions relevant for both post-combustion and pre-combustion applications.
Keywords	Membrane; CO2 separation; molten carbonate; dual-phase membrane; ionic conductor
Remark	Link

ID=202

Metallic Interconnects for Proton Ceramic Fuel Cells. Oxidation behavior and transport properties under simulated fuel cell conditions

Author	Anders Werner Bredvei Skilbred
Source	Time of Publication: 2013-03
Remark	Dissertation for the degree of Philosophiae Doctor Link

ID=190

Investigation of La1−xSrxCrO3−∂ (x ~ 0.1) as Membrane for Hydrogen Production

Authors	Yngve Larring, Camilla Vigen, Florian Ahouanto, Marie-Laure Fontaine, Thijs Peters, Jens B. Smith, Truls Norby and Rune Bredesen
Source	Membranes Volume: 2, Issue: 3, Pages: 665-686 Time of Publication: 2012-09
Abstract	Various inorganic membranes have demonstrated good capability to separate hydrogen from other gases at elevated temperatures. Hydrogen-permeable, dense, mixed proton-electron conducting ceramic oxides offer superior selectivity and thermal stability, but chemically robust candidates with higher ambipolar protonic and electronic conductivity are needed. In this work, we present for the first time the results of various investigations of La1−xSrxCrO3−∂ membranes for hydrogen production. We aim in particular to elucidate the material’s complex transport properties, involving co-ionic transport of oxide ions and protons, in addition to electron holes. This opens some new possibilities for efficient heat and mass transfer management in the production of hydrogen. Conductivity measurements as a function of pH2 at constant pO2 exhibit changes that reveal a significant hydration and presence of protons. The flux and production of hydrogen have been measured under different chemical gradients. In particular, the effect of water vapor in the feed and permeate gas stream sides was investigated with the aim of quantifying the ratio of hydrogen production by hydrogen flux from feed to permeate and oxygen flux the opposite way (“water splitting”). Deuterium labeling was used to unambiguously prove flux of hydrogen species.
Keywords	hydrogen transport membrane; proton permeation; oxygen permeation; water splitting
Remark	Link

ID=178

Nd-doped Ba(Ce,Zr)O3 − δ proton conductors for application in conversion of CO2 into liquid fuels

Authors	Wojciech Zając , Emil Hanc, Agnieszka Gorzkowska-Sobas, Konrad Świerczek, Janina Molenda
Source	Solid State Ionics Volume: 225, Pages: 297–303 Time of Publication: 2012-10
Abstract	The paper presents crystal structure, transport properties, chemical stability in CO2 atmosphere and thin film membrane preparation for materials from the Ba(Ce1 − xZrx)0.9Nd0.1O2.95 (x = 0, 0.25, 0.5, 0.75, 1) group of perovskite-type structure oxides. Transformation of crystal structure from orthorhombic Pnma to orthorhombic Imma and cubic with increasing xZr was observed along with linear decrease of pseudo-cubic unit cell volume and free lattice volume. Electrical conductivity of bulk and grain boundary was determined in dry air, as well as in air humidified with H2O or D2O. The highest proton conductivity was observed for material with xZr = 0.25. Further increase of Zr content led to decrease of conductivity as high as 2 orders of magnitude. This effect was coupled with bell-shape dependence of activation energy and pre-exponential term. Such behavior was explained as superimposed effects of high proton mobility for zirconium-rich materials due to cubic symmetry and cerium-rich materials due to softness of oxygen–oxygen separation distance, along with high proton concentration for cerium-rich perovskites. The deteriorating effect of grain boundaries on total electrical conductivity was far more pronounced for Zr-rich materials than in the case of Ce-rich ones. Declining grain boundary conductivity was attributed to both increase of number of grain boundaries and decrease of inherent grain boundary conductivity for Zr-rich samples. The highest chemical stability in CO2 atmosphere was achieved for high-Zr content materials, on the contrary, for BaCe0.9Nd0.1O2.95 in CO2 atmosphere, the decomposition onset temperature was below 500 °C. 2 μm thin film membrane of Ba(Ce0.75Zr0.25)0.9Nd0.1O2.95 was successfully prepared on c-plane sapphire and fused silica substrates. Film's crystal structure matched that of the bulk material. The electrical conductivity of thermally treated film obtained on c-plane sapphire in wet air was 3.7 × 10− 4 S cm− 1 at 600 °C.
Keywords	Proton conductors; BaCeO3–BaZrO3 solid solutions; Isotope effect; Grain boundary effect; Thin films
Remark	Link

ID=176

Hydrogen permeation, transport properties and microstructure of Ca-doped LaNbO4 and LaNb3O9 composites

Authors	Wen Xing, Guttorm E. Syvertsen, Tor Grande, Zuoan Li, Reidar Haugsrud
Source	Journal of Membrane Science Volume: 415-416, Pages: 878–885 Time of Publication: 2012-10
Abstract	Two composites consisting of the proton conducting Ca-doped LaNbO4 and electron conducting LaNb3O9 with respectively 90 and 70 vol% LaNbO4 were prepared by spark plasma sintering. The amount of hydrogen produced at the sweep side was measured as a function of temperature and pH2 gradient under wet and dry sweep gas conditions. The hydrogen flux increases with increasing temperature and feed-sidepH2. The flux is significantly higher for the 70 vol% LaNbO4 composite than the 90 vol% LaNbO4 composite. Ambipolar conductivities calculated from the flux data showed the same pH2 dependence for both composites. The electrical conductivity of the 70 vol% LaNbO4 composite was characterized as a function of temperature under wet hydrogen. The microstructure and phase distribution of the two composites are analyzed and their transport properties with different flux limiting processes are discussed. An increased hydrogen production with wet compared to dry sweep gas is concluded to reflect water splitting due to transport of oxygen from the permeate to the feed side.
Keywords	Hydrogen flux; Proton conductivity; Ceramic-ceramic composite; LaNbO4; LaNb3O9; Ambipolar conductivity; Water splitting
Remark	Link

ID=168

Synthesis, Sintering, Transport Properties, and Surface Exchange of La2Ni0.9Cu0.1O4+δ

Authors	Zuoan Li, Truls Norby, Reidar Haugsrud
Source	Journal of the American Ceramic Society Volume: 95, Issue: 6, Pages: 2065–2073 Time of Publication: 2012-06
Abstract	Dense La2Ni0.9Cu0.1O4+δ ceramics were sintered from powders synthesized through a wet-chemical citrate nitrate route with optimized ratios of citrate to nitrate. Less citrate decreases the required sintering temperature and improves the oxygen permeativity. The oxygen permeation was measured as a function of oxygen activity gradient, membrane thickness (0.4–2.6 mm) and temperature (800°C–950°C). The oxygen self diffusion coefficient DO and the surface exchange coefficient k show Arrhenius-type behaviors with activation energies of ~50 and ~100 kJ/mol, respectively. The oxygen chemical diffusion coefficient Dchem and surface exchange coefficient kchem, measured by conductivity relaxation, exhibit Arrhenius-type behaviors with activation energies of 62 and 104 kJ/mol, respectively. Dchem and kchem are related to DO and k through the thermodynamic factor ωO.
Remark	Link

ID=141

Influence of Pr substitution on defects, transport, and grain boundary properties of acceptor-doped BaZrO3

Authors
Source	International Journal of Hydrogen Energy Volume: 37, Issue: 9, Pages: 7962–7969 Time of Publication: 2012-05
Abstract	We report on effects of partially substituting Zr with the multivalent Pr on the conductivity characteristics of acceptor (Gd) doped BaZrO3-based materials. BaZr0.6Pr0.3Gd0.1O3−δ was sintered 96% dense at 1550 °C with grains of 1–4 μm. The electrical conductivity was characterised by impedance spectroscopy and EMF transport number measurements as a function of temperature and the partial pressures of oxygen and water vapour. H2O/D2O exchanges were applied to further verify proton conduction. The material is mainly a mixed proton–electron conductor: the p-type electronic conductivity is ∼0.004 and ∼0.05 S/cm in wet O2 at 500 and 900 °C, respectively, while the protonic conductivity is ∼10−4 S/cm and ∼10−3 S/cm. The material is expectedly a pure proton conductor at sufficiently low temperatures and wet conditions. The specific grain boundary conductivity is essentially equal for the material with or without Pr, but the overall resistance is significantly lower for the former. We propose that replacing Pr on the Zr site reduces the grain boundary contribution due to an increased grain size after otherwise equal sintering conditions.
Keywords	BaZrO3; BaPrO3; Defects and transport; Grain boundaries; Grain boundary specific conductivity
Remark	Link

ID=128

Proton Conductivity in Acceptor-Doped LaVO4

Authors	Morten Huse, Truls Norby, and Reidar Haugsrud
Source	J. Electrochem. Soc. Volume: 158, Issue: 8, Pages: B857-B865 Time of Publication: 2011-06
Abstract	Electrical characterization of nominally undoped LaVO4, La0.99Ca0.01VO4− and La0.95Ca0.05VO4− was performed in various partial pressures of oxygen, water vapor and hydrogen isotopes, from 300 to 1100°C by impedance spectroscopy, AC conductivity measurements (10 kHz) and EMF-measurements. XRD, SEM and EDS were used for structural, micro structural and compositional analysis. Acceptor doped LaVO4 is a pure ionic conductor in oxidizing atmospheres in the entire measured temperature range; dominated by proton conductivity at low temperatures (T < 450°C) under wet conditions and oxide ion conductivity at high temperatures. A maximum in the partial proton conductivity of ~ 6 × 10−5 S/cm was reached at 900°C (pH2O2.5·10-2 atm). Thermodynamics of hydration and transport parameters for charge carriers in La0.99Ca0.01VO4 were derived from relations between defect chemistry, transport properties and the measured conductivity data and revealed: S=− 130 ± 10 J/mol K, S =− 142 ± 10 J/mol K, H=− 110 ± 10 kJ/mol, µ0,H+ = 50 ± 6 cm2 K/Vs, Hmob,H+ = 75 ± 10 kJ/mol, µ0,v= 120 ± 20 cm2 K/Vs and Hmob,v = 85 ± 10 kJ/mol. The tetrahedron (XO4) volume and migration enthalpy were found to be correlated for the series of monoclinic LaXO4.

ID=120

Conductivity, transport number measurements and hydration thermodynamics of BaCe0.2Zr0.7Y(0.1 − ξ)NiξO(3 − δ)

Authors	S. Ricotea, The Corresponding Author, N. Bonanos, H.J. Wang and R. Haugsrud
Source	Solid State Ionics Volume: 185, Issue: 1, Pages: 11-17 Time of Publication: 2011-03
Abstract	BaCe0.2Zr0.7Y(0.1 − ξ)NiξO(3 − δ) compounds with ξ = 0.01 and 0.02 have been synthesized by solid state reaction at 1400 °C and sintered at 1450 °C. TEM analyses were performed and showed a segregation of nickel at the grain boundaries for ξ = 0.02. This apparent solubility limit of Ni in the B-site of the perovskite is in agreement with similar data obtained earlier for the two compositions. The first aim of this work was to evaluate the conductivity of BaCe0.2Zr0.7Y(0.1 − ξ)NiξO(3 − δ) at temperature between 500 and 900 °C, using impedance spectroscopy at different oxygen partial pressures and water vapor pressures, as well as the emf technique. The compounds exhibit p-type conduction in oxidizing atmosphere, and ionic conduction elsewhere. The oxide ion contribution of the conductivity is negligible only for temperatures below 600 °C. The determination of hydration enthalpies, our second goal, was achieved by modelling of the conductivity data and by thermogravimetric measurements (TG-DSC).

ID=103

Defects and transport properties of Sr-doped LaP3O9

Authors	Vajeeston Nalini, Reidar Haugsrud and Truls Norby
Source	Solid State Ionics Volume: 181, Issue: 27-28, Pages: 1264-1269 Time of Publication: 2010-09
Abstract	LaP3O9 and 2 mol-% Sr-doped LaP3O9 have been synthesized by the solid-state reaction method and the phase purity was characterized by powder X-ray diffraction and scanning electron microscopy. The AC conductivity of sintered disks was measured with two-point electrode setup in the temperature range 300 − 700 °C under oxidizing and reducing conditions at different oxygen and water vapor (H2O or D2O) partial pressures by means of impedance spectroscopy. The water vapor dependency and isotope effect reveal that protons are the predominant charge carrier. The conductivity was mainly independent of the partial pressure of oxygen at all measured temperatures under both oxidizing and reducing conditions, suggesting only minor electronic conductivity. Hydration thermodynamics and transport parameters for the Sr-doped sample have been determined based on a defect chemical model applied to thermogravimetry and conductivity data.
Keywords	Proton conductivity; LaP3O9; Sr-doped LaP3O9; Defect structure; Thermodynamic relations; Transport parameters

ID=85

Defects and transport properties in Ln6WO12 (Ln = La, Nd, Gd, Er)

Author	Reidar Haugsrud
Source	Solid State Ionics Volume: 178, Issue: 7-10, Pages: 555-560 Time of Publication: 2007

ID=66

Transport properties and defect analysis of La1.9Sr0.1NiO4 + δ

Authors	Zuoan Li, Reidar Haugsrud, Jens B. Smith and Truls Norby
Source	Solid State Ionics Volume: 180, Issue: 26-27, Pages: 1433-1441 Time of Publication: 2009

ID=30

Transport numbers from hydrogen concentration cells over different oxides under oxidising and reducing conditions

Authors
Source	Pages: 3147-3151 Time of Publication: 2004
Remark	Disk samples: 2-electrode AC conductivity, transport numbers of hydrogen ions by EMF of hydrogen concentration cell

ID=29

Conductivity dependence on oxygen partial pressure and oxide-ion transport numbers determination for La2Mo2O9

Authors
Source	Electrochemical and Solid-State Letters Volume: 10, Issue: 7, Pages: A373-375 Time of Publication: 2004
Remark	Disk samples: 4-point van der Pauw conductivity, 2-electrode impedance spectroscopy, transport numbers of oxygen ions by EMF of oxygen concentration cell

ID=28

Impedance spectroscopy and proton transport number measurements on Sr-substituted LaPO4 prepared by combustion synthesis

Authors
Source	Solid State Ionics Volume: 162-163, Pages: 167-173 Time of Publication: 2003
Remark	Disk samples: 2-electrode AC conductivity, transport numbers of protons by EMF of hydrogen concentration cell

ID=10

Electrical conductivity and ionic transport number of YSZ and Cr-doped YSZ single crystals at 200-1000°C

Authors
Source	Solid State Ionics Volume: 67, Pages: 57-64 Time of Publication: 1993
Remark	Small single crystals, Pt paint electrodes, placed over small hole in support plate to form concentration cell. Role of sample holder parasitic conductance evaluated.