Conductivity and expansion at high temperature in Sr_0.7La _0.3TiO_3-α prepared under reducing atmosphere

Sr_0.7La_0.3TiO_3-α specimens were prepared in reducing atmosphere, and the structural and electrical properties were studied. The lattice parameter of Sr_0.7La_0.3TiO _3-α at room temperature was larger than that expected from Vegard's law between SrTiO₃ and LaTiO₃ due to the reductive expansion. The conductivity of this specimen was 100 S cm^-1 at 1000°C, p _{O 2} = 10^-13 Pa. However, the conductivity was not preserved after an oxidation-reduction cycle. Over p _{O 2} = 10² Pa, the conductivity drastically dropped with increasing p _{O 2}. The thermal expansion coefficient of Sr_0.7La_0.3TiO_3-α was 11.8 × 10^-6 K^-1 in 9% H₂/N₂ (room temperature - 1000°C). In this Sr_0.7La_0.3TiO _3-α, the chemical expansion on oxidation reached Δl/l_o = 0.51%, when changing p _{O 2} from 10^-11 Pa to 2 × 10⁴ Pa (air) at 1000°C.