Doping effect on secondary phases, microstructure and electrical conductivities of LaGaO3 based perovskites

The intermediate temperature electrolytes La1−xSrxGa1−yMgyO3−δ (LSGM, where δ = (x + y)/2) with perovskite structure were prepared using a poly(vinyl alcohol) (PVA) solution polymerization method. Three secondary phases were identified by X-ray diffraction, LaSrGaO4, LaSrGa3O7 and La4Ga2O9. The relative amount of these secondary phases depended on the doping compositions. Sr doping produced more Sr rich secondary phases with increasing content, while enhanced solid solubility was observed with Mg addition. Sintered samples showed dense microstructures with well-developed equiaxed grains, and the secondary phases were mainly in the grain boundaries. LaSrGaO4 could not be detected by SEM for the sintered pellets. The oxygen ionic conductivity was enhanced by doping with Sr and Mg. Mg doping showed the increased conductivity activation energy. La0.8Sr0.2Ga0.9Mg0.1O2.85 had the highest ionic conductivity σ = 0.128 S/cm at 800 °C in this work.