Interfacial reaction between YSZ electrolyte and La _0.7 Sr _0.3 VO ₃ perovskite anode for application

The synthesis and performance of La _0.7 Sr _0.3 VO ₃ /YSZ composites are investigated as alternative anodes for the direct utilization of methane (i.e., biogas) in solid oxide fuel cells. In this study, the structural stability between Sr-doped lanthanum vanadate and yttria-stabilized zirconia was investigated by using the powder mixture annealed at various periods of time and temperatures. The chemical reaction between these two materials in the temperature ranging from 1100 to 1400 °C was examined by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) analyses. According to the examination of La _0.7 Sr _0.3 VO ₃ /YSZ powder mixture after heat treatment at 1100–1400 °C, no second phase was detected when the La _0.7 Sr _0.3 VO ₃ /YSZ powder mixture was heated at 1100 °C. The reaction products of perovskite SrZrO ₃ were formed when the specimens were heated treatment at over 1200 °C. Owing to the further diffusion of Sr cations from La _0.7 Sr _0.3 VO ₃ toward the reaction layer/YSZ interface via the reaction layer, the reaction layer was extended into the YSZ. The interfacial reaction behavior between electrode and electrolyte pellets of the reaction couple was examined by EPMA. No reaction products were observed as La _0.7 Sr _0.3 VO ₃ /YSZ composite co-fired at 1100 °C. The reaction products of perovskite SrZrO ₃ were formed when the specimens were heat treated at over 1200 °C. The bonding energy between La-O (188 kcal/mol) is stronger than Sr-O (83.6 kcal/mol). Thus, Sr ions tend to migrate and react with YSZ much faster than La ions. Furthermore, when the Sr concentration increases to 70%, excess of SrZrO ₃ formation leads to the phase decomposition of perovskite La _0.3 Sr _0.7 VO ₃ .