Structure, conductivity and redox reversibility of Ca-doped cerium metavanadate

Abstract

A-site substituted cerium metavanadates, Ce1−xCaxVO3,were synthesised by solid-state reactions from single-phase powders of the corresponding orthovanadates. All metavanadate samples were found to exhibit either an orthorhombic and/or monoclinic phase of space groupPnma (62) with a = 5.5067 (4), b = 7.7904 (5) and c = 5.4814(7) A for Ce0.8Ca0.2VO3. X-Ray diffraction patterns and thermal analyses have shown that the reduction of Ca-doped CeVO3 from the equivalent orthovanadate is redox phase reversible without formation of parasitic phases at x = 0.2, 0.3. Conductivity measurements were performed in air and in dry 5% H2–Ar with conductivity of Ce1−xCaxVO3 ranging from 1.5 to 13 S cm−1 at 700 °C in a reducing atmosphere. Sample Ce0.7Ca0.3VO3 exhibits the highest conductivity in a reducing atmosphere in all the measured samples which could be a potential anode or as a part of composite anode for SOFCs. The conductivity of Ce0.7Ca0.3VO3 is higher than that for Ce0.85Sr0.15VO3 which could be related to the higher doping level.