Transport properties and thermal expansion of La2Mo2O9-based solid electrolytes |
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Authors: | I.P. Marozau V.V. Kharton N.P. Vyshatko J.R. Frade |
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Affiliation: | a Institute of Physicochemical Problems, Belarus State University, 14 Leningradskaya Str., 220050 Minsk, Belarus b Department of Ceramics and Glass Engineering, CICECO, Campus de Santiago, University of Aveiro, 3810-193 Aveiro, Portugal |
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Abstract: | The oxygen ion transference numbers of La1.7Bi0.3Mo2O9, La2Mo1.7W0.3O9 and La2Mo1.95V0.05O9 ceramics, determined by modified faradaic efficiency and e.m.f. methods at 973-1173 K, vary in the range 0.995-0.977 in air, decreasing when temperature increases. The activation energies for the ionic and electronic transport are 61-71 kJ/mol and 123-141 kJ/mol, respectively. Reducing oxygen chemical potential leads to increasing n-type electronic contribution to the total conductivity, which remains, however, essentially p(O2)-independent down to oxygen pressures of 10−4-10−3 atm and exhibits reversible drop on further reduction, probably due to phase decomposition. Doping La2Mo2O9 with calcium results in segregation of a CaMoO4-based phase, accompanied with increasing electronic transport. The average thermal expansion coefficients of La2Mo2O9-based materials, calculated from dilatometric data in air, are (14.4-14.8) × 10−6 K−1 at 300-700 K and (16.4-22.5) × 10−6 K−1 at 700-1070 K. |
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Keywords: | A. Oxides A. Ceramics D. Electrical properties D. Ionic conductivity D. Thermal expansion |
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