Phase formation and electrical conductivity of Ba-doped LaScO₃

Phase formation and conduction behavior in BaO-doped LaScO₃with the perovskite structure have been investigated. The structures of La _1-xBa_xScO_3-δ were analyzed to be cubic for La_0.6Ba_0.4ScO_1-δ and La _0.5Ba_0.5ScO_3-δ, a mixture of cubic and orthorhombic for La_0.9Ba_0.1ScO_3-δ, La_0.8Ba_0.2ScO_3-δ and La _0.7Ba_0.3ScO_3-δ, and orthorhombic for La_0.95Ba_0.05ScO_3-δ. La _1-xBa_xScO_3-δ showed a pure oxide-ion conduction below intermediate oxygen partial pressures under dry atmosphere. At high oxygen partial pressures, it exhibited mixed oxide-ion and p-type electronic conduction. In the presence of water vapor, proton conduction was observed due to the formation of protonic defects and the bulk conductivity by protons was highest in the composition of La_0.5Ba _0.5ScO_2.75. The apparent activation energy for proton conduction was almost the same in each compound, 0.66-0.68 eV, despite the differences in crystal structure and A-site dopant concentration.