The conductivity of La0.90Sr0.10Ga0.90Mg0.10O2.90 was measured from 1430K to room temperature by combining 4-point van der Pauw measurements (high temperatures) with two-point impedance spectroscopy (intermediate and low temperatures). At intermediate and low temperatures, samples with differing grain sizes were studied in order to look for fast conduction in the grain boundaries (in parallel). No fast grain boundary transport was detected. The conductivity data were modelled well by a defect association model involving Mg dopant–O vacancy clusters. The derived entropy and enthalpy of association were −73 and −80kJ/mol for this association pair, and the enthalpy of migration of the unassociated O vacancies was 58kJ/mol. The model was tested on measured high to intermediate temperature conductivities of LaGaO3 with lower dopant concentrations. The model was found to describe well the conductivity of La0.95Sr0.05Ga0.95Mg0.05O2.95, but it failed to describe the intermediate temperature conductivities of the sample of La0.99Sr0.01Ga0.99Mg0.01O2.99.

Temperature Dependence of Oxygen Ion Transport in Sr+Mg-Substituted LaGaO3 (LSGM) with Varying Grain Sizes. C.Haavik, E.M.Ottesen, K.Nomura, J.A.Kilner, T.Norby: Solid State Ionics, 2004, 174[1-4], 233-43