Ca-substituted, A-site deficient perovskite La_0.2Sr_0.7TiO₃ as a potential anode material for SOFCs

Samples from across the solid solution series La0.2Sr0.7-xCaxTiO3, were successfully synthesised by solid state reaction. Structural properties were determined at room temperature using X-ray powder diffraction and conductivity measurements were performed using the four probe DC and van der Pauw techniques at different temperatures and atmospheres. On increasing x, the perovskite phase lattice symmetry changes from cubic Pm (3) over barm to tetragonal I4/mcm at x = 0.05 and tetragonal to orthorhombic Pbnm at x = 0.425. The lattice also shrinks as x increases. Samples showed only a slight 0.3% increase in lattice volume after reduction at 900 degrees C in 5% H-2. On increasing calcium doping, conductivity in reduced samples and equilibrated at 900 degrees C in 5%H-2 increased markedly reaching 27.53 S cm(-1) at x = 0.45, but decreased as x increased further.