Optimized La1-xSrxGa1-yMgyO3-δ (0.1 ≤ x, y ≤ 0.3) electrolytes for solid oxide fuel cells applications: Synthesis, structural characterization and properties

This study explores the synthesis, structural characterization and properties of five different La1-xSrxGa1-yMgyO3-? (0.1 ? x,y ? 0.3) samples. Precursor powders were synthesized via the Pechini method and the corresponding ceramic samples were obtained by pressing under vacuum at 210MPa and sintering in air at 1300?C for 10 h. XRD analyses of the powders calcined at 1300?C and the samples sintered at 1300 ?C for 10 h confirmed predominance of cubic (Pm3m) perovskite structure, except for the La0.9Sr0.1Ga0.8Mg0.2O3-?, which exhibited a high amount of monoclinic phase. The presence of secondary phases was confirmed in the sample calcined at lower temperature, but also in four samples heated at 1300?C. A single-phase material was produced only in the case of the LSGM with x = 0.1 and y = 0.2. SEM revealed polygonal grains in the Sr-doped samples and spherical grains in the Mg-doped ones, with Mg improving sinterability and homogeneity. Conductivity increased with Sr and Mg doping (e.g. 0.12 S/cm at 800?C for La0.8Sr0.2Ga0.8Mg0.2O3-?), but secondary phases and lattice distortions affected ion transport. Thermal expansion rose by 23% with Mg doping yet decreased by 13% with Sr substitution.