Microstructure and electrical conductivity of fast fired Sr- and Mg-doped lanthanum gallate

La0.9Sr0.1Ga0.8Mg0.2O3−δ solid electrolytes were consolidated by fast firing aiming to investigate the effects of the sintering method on densification, microstructure and ionic conductivity. Powder mixtures were prepared by solid state reaction at 1250 and 1350 °C for 12 h, and fast fired at 1450 and 1500 °C temperatures for 5 and 10 min. The content of impurity phases was found to be quite low with this sintering method. Relatively high density (>90% of the theoretical value) and low porosity (<1.5%) were readily obtained for powder mixtures calcined at 1250 °C. The activation energy for conduction was approximately 1 eV. Specimens fast fired at 1450 °C for 10 min with a mean grain size of 2.26 µm reached the highest value of total ionic conductivity, 22 mS cm−1, at 600 °C.