Analysis of the microstructure and physical properties of La0.85Sr0.15Ga0.8Mg0.2O2.825 and Ce0.85Sm0.15O1.925 composite electrolytes used in solid oxide fuel cells

(100-x wt%) La0.85Sr0.15Ga0.8Mg0.2O2.825 (LSGM1520) + (x wt%) Ce0.85Sm0.15O1.925 (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 95 wt% LSGM1520-5 wt% SDC15, based on a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428) cathode and Ce0.8Sm0.2O1.9-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 264 mW/cm2 and 1.00 A/cm2 at 774 °C, and 182 mW/cm2 and 0.97 A/cm2 at 789 °C, respectively, and their open circuit voltages (OCV) are ∼1.0-1.1 V.