An oxide ion conducting La excess La1+xSr1-xGa3O7+δ (x = 0.05) was prepared by the high temperature ceramic route at 1350C in air and characterized by powder X-ray diffraction, energy-dispersive analysis by X-ray and thermogravimetric techniques to establish the phase purity, composition and amount of O excess respectively. The value of ‘δ’ was found to be 0.025. The a and c parameters were evaluated from the high temperature X-ray diffraction patterns and indicated non-linear behaviour with a gradual increase up to 600C and a steep increase thereafter. The thermal expansion coefficient (α) was calculated to be 8.285 x 10−6/K valid at 35 to 1000C. Electrical property measurements were carried out on 96% dense pellets and the bulk conductivity of La1.05Sr0.95Ga3O7.025 obtained from AC impedance studies was approximately two and three orders of magnitude less than YSZ and LSGM, respectively. Oxygen diffusion data were obtained by isotopic anneals followed by SIMS line scanning. The tracer diffusion coefficient (D*) and surface exchange coefficient (k*) calculated from the diffusion profile increased with increasing temperature. Reasonable agreement was established between the measured bulk conductivity and the contribution to conductivity from the oxide ions demonstrating oxide ion conduction.

Electrical Conductivity, Oxygen Diffusion and Surface Exchange Studies on a Melilite-Type La1.05Sr0.95Ga3O7+δ. E.S.Raj, S.J.Skinner, J.A.Kilner: Solid State Ionics, 2005, 176[11-12], 1097-101