Analysis of the microstructure and physical properties of La_0.85Sr_0.15Ga_0.8Mg_0.2O_2.825 and Ce_0.85Sm_0.15O_1.925 composite electrolytes used in solid oxide fuel cells

(100-xwt%) La_0.85Sr_0.15Ga_0.8Mg_0.2O_2.825 (LSGM1520)+(xwt%) Ce_0.85Sm_0.15O_1.925 (SDC15)(x=0, 2, 5, 7, 10, and 100) composite electrolytes were synthesized by a solid-state reaction. The microstructures and electrical properties of the electrolytes were analyzed by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy, thermomechanical analysis, and impedance spectroscopy. The electrolytes, LSGM1520 and 95wt% LSGM1520-5wt% SDC15, based on a La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) cathode and Ce_0.8Sm_0.2O_1.9-Ni (SDC20-Ni) cathode were used to form two SOFCs. The thermal expansion coefficients of the composites ranged from 10.5×10^-6/°C to 12×10^-6/°C at 200-600°C and 12×10^-6/°C to 15×10^-6/°C at 600-800°C. The performances and current density of LSCF6428/LSGM1520/SDC20-Ni and LSCF6428/95L05S/SDC20-Ni are 264mW/cm² and 1.00A/cm² at 774°C, and 182mW/cm² and 0.97A/cm² at 789°C, respectively, and their open circuit voltages (OCV) are ~1.0-1.1V.