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

Abstract

A-site substituted cerium metavanadates, Ce_1−xCa_xVO₃,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) Å for Ce_0.8Ca_0.2VO₃. 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 Ce_1−xCa_xVO₃ ranging from 1.5 to 13 S cm⁻¹ at 700 °C in a reducing atmosphere. Sample Ce_0.7Ca_0.3VO₃ 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 Ce_0.7Ca_0.3VO₃ is higher than that for Ce_0.85Sr_0.15VO₃ which could be related to the higher doping level.