Space Charge Effects on the Interfacial Conduction in Sr-Doped Lanthanum Gallates: A Quantitative Analysis

The origin of the blocking effects of the grain boundary on the electrical conduction in 1 mol % Sr-doped LaGaO 3 has been investigated. The oxygen partial pressure and the temperature dependences of the partial electronic and ionic conductivities of the grain boundary have been quantitatively analyzed based on the space charge models. The Mott−Schottky model has accurately reproduced those conductivity behaviors. The results clearly demonstrate that the space charge controls the grain boundary conduction in the material. The space charge potential estimated was about 0.4 V. Owing to the higher effective charge of the oxygen vacancy compared to that of the electron−hole leading to more severe depletion in the space charge zone, the electron−hole transference number increases in the space charge zone such that the grain boundary becomes mixed conducting, while the bulk is predominantly ionic conducting as experimentally observed.