Microstructure and electrical conductivity of sol-gel synthesized and spark plasma sintered doped-lanthanum gallate

Abstract

Perovskite ceramics consisting of lanthanum gallate with partial substitutions for strontium and magnesium are candidates as solid electrolyte for application in solid oxide fuel cells operating at intermediate temperatures (~550 to ~750ºC). The main concern related to the application of this perovskite solid electrolyte is impurity phases, usually detected even in chemically synthesized powders. The La0.9Sr0.1Ga0.8Mg0.2O3-d (LSGM) composition display relatively low contents of impurity phases. In this work, the LSGM composition was synthesized by the sol-gel method and consolidated by spark plasma sintering to optimize the microstructure and electrical properties of this solid electrolyte. Chemically synthesized powders were consolidated in the 1100 to 1250ºC for 5 min. Sintered specimens with relative densities higher than 98% were obtained. Rietveld analysis of X-ray diffraction data revealed no detectable impurity phases. The microstructure evolution exhibited submicron sized grains with mixed fracture mode. High values of the electrical conductivity were obtained for all specimens.