Processing and characterization of Sr2-xVMoO6-δ double perovskites

In this study, the analysis and characterization of the processing and sintering of Sr2-xVMoO6-delta perovskites, where x = 0.0, 0.1 and 0.2, was investigated with application potential in high temperature fuel cell electrodes and electro-catalysts. Sr2-xVMoO6-delta substrates were sintered in a reducing (5%H-2 95% N-2) atmosphere at 1100 degrees C, 1200 degrees C, and 1300 degrees C. The X-ray diffraction patterns indicate that the double perovskite is the primary phase for Sr2-xVMoO6-delta pellets sintered at 1200 degrees C and 1300 degrees C for 20 h; however, these pellets show a secondary phase of SrMoO4-delta. X-ray photoelectron spectroscopy revealed a deficiency of vanadium on the pellet surfaces, in which samples yielded surface vanadium concentrations of less than 5%. The vanadium inhomogeneity can be explained by the formation of the SrMoO4-delta scheelite phase (ABO(4)) due to oxygen exposure on the surface of the pellets, which indicates inward vanadium migration to the bulk, and was exhibited in redox cycling. Sr2-xVMoO6-delta pellets sintered at 1300 degrees C showed the lowest resistivity at both SOFC operating temperature (800 degrees C) and room temperature. The resistivity tests also show a semiconductor to metallic transition for all double perovskites, from heating up to 800 degrees C to cooling down to room temperature in a reducing atmosphere, related to the reduction of Mo6+ to Mo4+. Published by Elsevier B.V.