Conductivity and expansion at high temperature in Sr0.7La0.3TiO3-α prepared under reducing atmosphere

Sr0.7La0.3TiO3-alpha specimens were prepared in reducing atmosphere, and the structural and electrical properties were studied. The lattice parameter of Sr0.7La0.3TiO3-alpha 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 at 1000 C, pO2 = 10 exp(-13) Pa. The conductivity was not preserved after an oxidation-reduction cycle. Over pO2 = 100 Pa, the conductivity drastically dropped with increasing pO2. The thermal expansion coefficient of Sr0.7La0.3TiO3-alpha was 11.8 x 10 exp(-6)/K in 9% H2/N2 (room temperature to 1000 C). In this Sr0.7La0.3TiO3-alpha, the chemical expansion on oxidation reached Deltal/lo = 0.51%, when changing pO2 from 10 exp(-11) Pa to 20000 Pa (air) at 1000 C. 23 refs.