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

Abstract

This study explores the synthesis, structural characterization and properties of five different La1-xSrxGa1-yMgyO3-δ (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 210 MPa 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-δ, 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-δ), but secondary phases and lattice distortions affected ion transport. Thermal expansion rose by 23% with Mg doping yet decreased by 13% with Sr substitution.