Doping effect on crystal structure and conduction property of fast oxide ion conductor LaGaO 3-based perovskite

Abstract

In order to discuss oxide ion conduction mechanism for LaGaO 3-based perovskite compounds, doping effects were investigated using two kinds of solid solutions whose oxygen vacancy concentrations are the same: one is La 0.9Sr 0.1Ga 0.9Mg 0.1O 2.9 with A-site and B-site substitutions and the other is LaGa 0.8Mg 0.2O 2.9 with only B-site substitution. Conductivity measurements showed that La 0.9Sr 0.1Ga 0.9Mg 0.1O 2.9 had a circumstance whereby oxide ion could more easily diffuse in the perovskite structure than in LaGa 0.8Mg 0.2O 2.9. Structural analyses using neutron diffraction found out the following three differences: the first finding was that the saddle point formed by two A-site cations and one B-site cation in La 0.9Sr 0.1Ga 0.9Mg 0.1O 2.9 was larger than that in LaGa 0.8Mg 0.2O 2.9 due to larger displacements of A-site and B-site cations; the second was that the doubly doping with Sr and Mg was more effective for reduction of GaO 6 octahedral tilt angles than the doping with Mg; the last was that La 0.9Sr 0.1Ga 0.9Mg 0.1O 2.9 had larger oxygen displacement than LaGa 0.8Mg 0.2O 2.9. It was considered that these structurally related parameters dominated the high oxide ion conduction in LaGaO 3-based perovskite compounds.