Layered perovskites Sr1+xLa1-xAlO4-0.5x (x = 0.1, 0.2) with the Ruddlesden-Popper structure were synthesized by the combustion method (glycine-nitrate soft-chemistry technique) and investigated as potential oxide ion conductors for intermediate-temperature devices for electrochemical applications. X-ray diffraction analysis confirmed the formation of single-phase materials with tetragonal symmetry (space group I4/mmm). The introduction of Sr2+ cation in the place of La3+ leads to the creation of oxygen vacancies and a significant increase in ionic conductivity. At 600 °C, the total conductivity increased by factors of 270 and 40 for x = 0.1 and 0.2, respectively, compared to the undoped sample SrLaAlO4. The activation energy for oxygen ion transport decreased from 1.51 eV for the parent compound to 0.84 eV for the doped phases. The optimal Sr2+ doping level was determined to be 10 mol%, which provides the best balance between structural parameters (unit cell volume and free cell volume) and oxygen vacancy concentration. The bulk oxygen-ion conductivity at 700 °C for the sample Sr1.1La0.9AlO3.95 reaches 10-3 S cm⁻¹. All the studied phases are stable over a wide range of PO2(10-20 ‒0.68 atm) at 400‒900 oC. The present result endorses that the RP compounds based on aluminates are low-cost promising candidates for electrochemical devices.

The new donor-doped phase with hexagonal perovskite-related structure Ba7Sc5.90Zr0.10Al2O19.05 was obtained by Pechini method. The substitution of Sc3+ by Zr4+ was accompanied by the formation of oxygen interstitial defects in the hexagonal block, which led to a decrease in the degree of hydration (from 1 to 0.91 mol H2O). This is explained by the decrease in the number of available sites for the placement of OH-‒groups. At the same time, for dry conditions (pH2О = 3·10−5 atm) this led to an increase in oxygen-ion conductivity as a result of the appearance of additional charge carriers. This effect was accompanied by an increase in oxygen-ion conductivity by 1 order of magnitude at 300 °C and a decrease in energy activation from 0.5 to 0.2 eV. For wet conditions (pH2O=2·10−2 atm) the donor doping led to an increase in proton mobility, which was facilitated by the appearance of the defect and the effects of additional repulsion of like-charged and defects. As a result, the proton conductivity increased and reached significant values 3.7·10-3 at 425 °C. The investigated phase Ba7Sc5.90Zr0.10Al2O19.05 demonstrated the predominant protonic conductivity at Т500 °C.

Acceptor-doped LaScO3 is a promising proton conductor for intermediate-temperature applications. This work decouples the effects of dopant charge and size by co-doping: fixing the A-site acceptor at 10 mol% Ba2+ (the LBS composition) and varying the B-site aliovalent Mg2+ (size close to Sc3+) cation (the LBSMg composition) or isovalent Ga3+ (smaller, the LBSGa composition) and Y3+ (larger, the LBSY composition) cations. All three co-doped compositions exhibit the perovskite structure characteristic of LaScO3. Co-doping with Mg2+ yields the highest hydration degree (74% of the theoretical limit) and total conductivity (LBSMg > LBS > LBSY > LBSGa). Under wet atmospheres, proton transport dominates below 600 °C, with ΣtH+ = 0.9 for LBSMg. Optical band gap measurements show that co-doping reduces the gap compared to single-doped LBS, and the gap decreases with increasing B-site cation radius. Hydration lowers the band gap for LBS, LBSMg, LBSGa but increases it for LBSY, consistent with its lower hydration ability. Combined experimental and theoretical (Geometrical-topological, Bond Valence Site Energy, kinteic Monte-Carlo, Density Functional Theory) analysis provides insight into defect chemistry and ion migration. The Mg-containing sample is particularly attractive for applications requiring high proton selectivity, such as sensors or hydrogen separation membranes.

The thermal and electric properties of the Y3+-doped Ba7In5.9Y0.1Al2O19 phase with the hexagonal perovskite structure (a = 5.935(7) Å, c = 37.736(8) Å) are studied. It is shown that this phase can incorporate protons and exhibit protonic conduction. Upon addition of an isovalent dopant, yttrium, the concentration of protons increases (up to the limiting value for Ba7In5.9Y0.1Al2O19·0.55H2O), as a result of the increase in the unit cell volume and, correspondingly, in the free space for accommodating OH– groups in the oxygen-deficient block containing coordination-unsaturated polyhedrons [BaO9]. The isovalent doping increases the oxygen-ionic conductivity due to an increase in interatomic distances and a decrease in the activation energy of migration. In a humid atmosphere (pH2O = 1.92 × 10−2 atm), the Ba7In5.9Y0.1Al2O19 phase exhibits the higher values of protonic conductivity as compared with the matrix compound Ba7In6Al2O19 and below 500°C is characterized by the predominant proton transport both in air and in a wide pO2 region (10–18–0.21 atm).

The work aims to investigate the layered perovskite SrLaAlO4 with the Ruddlesden-Popper structure as a potential proton conductor for medium-temperature solid oxide fuel cells (SOFCs). The sample was synthesized using the glycerol-nitrate method with subsequent calcination of the sample at 1200 °C for 24 h. Electrical properties were studied in dry and humid atmospheres to confirm the presence of proton conductivity, which dominates at temperatures below 500 °C. The phase SrLaAlO4 is stable over a wide range of partial pressures of oxygen and at high partial pressures of water vapor. The degree of hydration reaches 0.16 mol H2O, which corresponds to the composition SrLaAlO3.84(OH)0.32. IR studies confirmed the presence of different types of OH−-groups participating in hydrogen bonds of varying strengths.

New materials based on LaScO3, namely, were synthesized by the solid-phase method. The structure of the resulting complex oxides was refined. The electrical properties of the undoped, mono- and co-doped samples were determined by varying the temperature T and pH2O. All substituted samples were found to have the conductivity of several orders of magnitude higher relative to the parent phase. The maximum conductivity was observed for the Ba2+/Mg2+-co-doped sample due to high concentration of oxygen vacancies The possibility of phase formation and its electrical properties are greatly influenced by geometric parameters such as the ratio of the radii of the host- and the dopant-ion, the free cell volume, the critical radius. It has been demonstrated that the nature of the dopant affects the porosity of the samples. The investigated phases demonstrate good chemical stability in a CO2-saturated atmosphere.

The structural and morphological properties of samples in the Ba2In2O5–Ba2InNbO6 eutectic system were studied when treated below and above the eutectic temperature. A narrow-extent Ba2In2-xNbxO5+x (х ≤ 0.05) solid solution and (1 − y)Ba2In1.95Nb0.05O5.05∙yBa2InNbO6 composites were found in the system. In the y ≥ 0.15 composites, the major phase is a stabilized structure with a disordered arrangement of oxygen vacancies. The total electrical conductivity in dry air is determined primarily by oxygen-ion transfer, and it increases for both the solid solution and the composites; the greatest increase of about two orders of magnitude is in the y = 0.15 and 0.25 composite samples treated at above-eutectic temperature. The increase in electrical conductivity is due to the combined influence of structural and morphological factors. The composites treated at above-eutectic temperature have a specific morphology. A layer of submicron-sized crystallites is formed on the surface of the grains of the major phase upon eutectic crystallization, which is responsible for the appearance of the composite electrical conductivity effect.

The crystal structure, TG-MS, IR, and hydration thermodynamic parameters of the inherently oxygen-deficient Ba7In6-x Y x Al2O19 system have been investigated. X-ray diffraction analysis showed that the Ba7In6-x Y x Al2O19 (0 <= x <= 0.25) are hexagonal perovskites belonging to the P63 /mmc space group. The hydrated materials exhibited the same structure with larger cell parameters. IR spectroscopy of the hydrated specimens confirmed the existence of three types of hydroxyl groups involved in different hydrogen bonds. The dissolution of water was measured by using thermogravimetric (TG) analysis. The TG measurements showed the water uptake growth with increase of x. Dehydration upon heating is a three-stage process, namely, two close effects in the temperature range 200-600 degrees C and a small high-temperature effect near 800 degrees C. A defect chemical model was developed to derive hydration thermodynamic parameters based on TG data. A thermodynamic approach to the hydration process showed that the increase in the Y3+ content was accompanied by a decrease in the enthalpy of hydration due to the enlargement in the basicity of the phases. The strategy of introducing an isovalent dopant with a larger size and lower electronegativity turned out to be favorable in terms of increasing the proton concentration and decreasing the enthalpy of hydration.

The novel phase Ba7In5.9Zn0.1Al2O18.95 with hexagonal perovskite structure was obtained by solid-state technique. The substitution of In3+ by the Zn2+ leads to the expansion of the lattice parameters and cell volume. It was established that the investigated sample is capable of water incorporation from the gas phase; the degree of hydration reaches 1.42 mol H2O, which is significantly higher than that for the undoped phase (0.41 mol H2O). This is a result of the expansion of the hexagonal layer that facilitates the placement of OH–-groups. The oxide-ion and proton conductivities for the doped Ba7In5.9Zn0.1Al2O18.95 sample were higher than those for the undoped composition, Ba7In6Al2O19, by 0.50 and 0.75 orders of magnitude (500 °C), respectively. The new phase Ba7In5.9Zn0.1Al2O18.95 demonstrates the predominant protonic conductivity at Т ≤ 500 °C and pH2O = 1.93·10−2 atm.

Co-doped LaInO3-based materials have been studied. Strontium-sustituted solid solutions have high conductivity values but exhibit a low level of oxygen deficiency. Mg2+ and Ca2+ ions have been selected as the B-sublattice co-dopant. Both series of the solid solutions—La0.9Sr0.1In1 – xCaxO2.95 – 0.5x and La0.9Sr0.1In1 – yMgyO2.95 – 0.5y—crystallize in orthorhombic symmetry with space group Pnma. Ionic conductivity in a dry atmosphere is determined by the transport of oxygen ions. Oxygen-ion transport in solid solutions is 30–40

This paper is devoted to the study of LaInO3 based co-doped materials. Solid solutions in which lanthanum is substituted for strontium have sufficiently high conductivity values, but a low level of oxygen deficiency is realized. Mg2+ and Ca2+ ions were chosen as co-dopants for the B sublattice. Both series of the investigated La0.9Sr0.1In1-xCaxO2.95–0.5x and La0.9Sr0.1In1-yMgyO2.95-0.5y solid solutions crystallize in orthorhombic symmetry with sp. gr. Pnma. The ionic conductivity in a dry atmosphere is determined by the oxygen ions transport. Oxygen-ion transfer in solid solutions is ~30–40% at high temperatures (T 700°C) and increases to 80% as the temperature decreases to 400–300°C. The substitution Ca2+ with In3+ increases the electrical conductivity of the oxygen ions; the highest values are achieved for the compositions La0.9Sr0.1In0.95Ca0.05O2.925 and La0.9Sr0.1In0.9Ca0.1O2.9. The introduction of Mg2+ co-dopant at the In3+ positions leads to a decrease in ionic conductivity compared to La0.9Sr0.1InO2.95. The effects of changing oxygen mobility with changing geometric factors (cell volume, critical radius) are discussed.

The solid solution Ba7In6-xYxAl2O19 (0 <= x <= 0.25) with a hexagonal perovskite-like structure was prepared by the solid-state route. The introduction of yttrium was accompanied by an increase in lattice parameters. The total conductivity as a function of p(O2) and T was measured at different humidity. The partial conductivities were found by transport number measurements and were fitted based on the defect formation model. Oxygen-ion and proton conductivities were found to increase with Y3+ content as a result of an increase in cell volume and free volume, which was accompanied by a decrease in the activation energy of both oxygen-ion and proton conductivity. Oxygen-ion conductivity and proton conductivity dominated below 500 degrees C in dry (p(H2O)=3.5x10(-5) atm) and in wet (p(H2O)=1.92x10(-2) atm) conditions, respectively. Doping makes it possible to increase proton conductivity by an order of magnitude (500 degrees C) and significantly increase the proton transport numbers. The prepared phases exhibited excellent chemical stability during thermal treatment in carbon dioxide (p(CO2)=1 atm).

The solid solution Ba5In2-xYxAl2ZrO13 (0 <& khcy;<0.50)with hexagonal structure (space group P 6 3 / mmc ) was prepared by the solid-state reaction method. The effects of isovalent Y3+-substitution on the structure, hydration, bandgap and transport properties have been investigated. The introduction of yttrium was accompanied by lattice expansion, which led to an increase in the concentration of protons during hydration. The doping did not lead to a significant increase in oxygen-ion conductivity since there was no change in oxygen stoichiometry. At the same time, doping led to an increase in ionic transport numbers due to a decrease in hole conductivity. Proton conductivity contribution and the values of proton conductivity increase with the increase in yttrium concentration. The phases with yttrium content x > 0.2 were predominant proton conductors at the temperature below 600 degrees & Scy; degrees & Scy; under wet air.

New materials based on LaScO3, namely, were synthesized by the solid-phase method. The structure of the resulting complex oxides was refined. The electrical properties of the undoped, mono- and co-doped samples were determined by varying the temperature T and pH2O. All substituted samples were found to have the conductivity of several orders of magnitude higher relative to the parent phase. The maximum conductivity was observed for the Ba2+/Mg2+-co-doped sample due to high concentration of oxygen vacancies The possibility of phase formation and its electrical properties are greatly influenced by geometric parameters such as the ratio of the radii of the host- and the dopant-ion, the free cell volume, the critical radius. It has been demonstrated that the nature of the dopant affects the porosity of the samples. The investigated phases demonstrate good chemical stability in a CO2-saturated atmosphere.

A CO2-stable, 2-stable, easily sintered proton-conducting oxide electrolytes based on solid solution Ba 7 In 6 Al 2- x Zn x O 19-0.5 x with hexagonal structure has been synthesized for the first time. Within the homogeneity region (0 <= x <= 0.10), there is an increase in unit cell parameters, cell volumes and free cell volumes. The addition of Zn2+ 2+ markedly improved the sinterability of the material. The relative density of the ceramics of the doped samples reached 95 % at lower sintering temperatures than the parent phase. The electrical conductivity was studied using electrochemical impedance spectroscopy. Upon doping the oxygen-ion conductivity increased by 0.25 orders of magnitude at 800 degrees C. Proton transport was predominant below 500 degrees C for a wet atmosphere (pH2O 2 O = 1.92 center dot 10-2 atm). The investigated phases Ba 7 In 6 Al 2- x Zn x O 19-0.5 x are capable of hydration and incorporate up to 1.45 mol H2O 2 O vs 0.41 mol H2O 2 O for the parent phase. The studied phases exhibit chemical resistance to CO2 2 under heat treatment at 600 degrees C. It was shown that solid solution Ba 7 In 6 Al 2- x Zn x O 19-0.5 x is a promising electrolyte material for intermediate-temperature fuel cells.

The search for novel functional ceramic materials with targeted properties is currently very important. Complex oxides with perovskite or perovskite-related structure are being considered for the production of electrochemical devices for the hydrogen energy ecosystem. Layered perovskites including based on BaLaInO4 4 are promising materials for proton-conducting electrolyte of solid oxide fuel cells. The idea of this work is to create a triple conductivity material based on BaLaInO4. 4 . In this work, the doping of the lanthanum sublattice with iron ions was carried out for the first time. The effect of doping on the structure, water uptake and electrical conductivity was investigated. It was shown that the introduction of iron ions into lanthanum sublattice changes the crystal lattice from orthorhombic to tetragonal structure. The water uptake is very small and it is 0.02 mol H2O 2 O per formula unit for BaLa0.9Fe0.1InO4-delta 0.9 Fe 0.1 InO 4-delta composition. Studies of the electrical properties have shown that the nature of conductivity is mixed hole/oxygen ionic at dry air and hole/oxygen ionic/protonic and wet air. The Fe-doped- composition can be considered as triple conducting materials and it is prospective as the electrode materials comparable with protonic electrolyte Ba 1.1 La 0.9 InO 3.95 .

The desire to use novel functional materials in electrochemical devices stimulates significant research in materials science. Сomplex oxides with a perovskite-like structure occupy a large niche among such materials. Solid solutions based on LaInO3 exhibit promising ionic conductor properties (O2–, H+) combined with high chemical stability. This review presents a comprehensive analysis of the physicochemical properties of doped LaInO3 materials. The structure and hydration processes of parent and doped compounds are discussed. The transport properties data were collected and summarized. Both the pure and the doped materials exhibit mixed ion-hole conductivity in dry air. All solid solutions based on LaInO3 are capable of reversible incorporation of water vapor due to their effective oxygen vacancy size close to ran~1.4 Å. Under elevated humidity conditions, proton transfer is observed in the samples. The data indicates a correlation between an increase in free cell volume and an increase in ionic conductivity. The results on chemical stability and TEC for the pure and doped materials are analyzed. The strategy for selecting dopant cations is shown. The presented data show the potential for applications of LaInO3-based materials in electrolyte membranes for solid oxide fuel cells, pumps and sensors.

Proton conducting materials are used in electrochemical devices such as proton conducting fuel cells and proton conducting electrolyzers. These devices belong to the hydrogen energy field and serve the goals of clean energy and sustainable environmental development. Layered perovskites are a promising class of proton conducting electrolytes. Cationic co-doping is a well-known method to improve the transport properties of classical perovskite ABO3. However, data on the application of this method to layered perovskites are limited. In this work, the bilayered perovskites BaLa1.9−xSrxGd0.1In2O7−0.5x have been prepared and studied for the first time. The possibility of oxygen-ionic and proton transport was demonstrated. Cationic co-doping was shown to increase the proton conductivity values by up to 1.5 orders of magnitude.

Proton-conducting electrochemical devices such as protonic ceramic fuel cells and protonic ceramic electrolysis cells play a major role in the creation of eco-friendly "green" energy systems. The most studies of proton-conducting materials for these devices are barium cerate zirconates. The layered perovskites are novel class of proton-conducting materials. In this paper, the possibility of cation and oxyanion doping of layered perovskite BaNd2In2O7 was carried out for the first time. The most conductive composition BaLa1.9Sr0.1In2O6.95 demonstrates protonic conductivity value 2$10-5 S/cm at 450 & DEG;C. The acceptor-doped two-layer perovskites are the prospective class of proton-conducting materials, and further modification of their composition opens up a new way in the design of solid oxide protonic conductors. & COPY; 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.