Microstructure and electrical conductivity of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 2.85 ‐Ce 0.8 Gd 0.2 O 1.9 composite electrolytes for SOFC s

(100‐ x ) wt.% La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 ‐ x wt.% Ce 0.8 Gd 0.2 O 1.9 ( x  =   0, 5, 10, 20) electrolytes were prepared by solid‐state reaction. The composition, microstructure, and electrical conductivity of the samples were investigated. At 300 ~ 600°C, the pure La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 electrolyte has a higher conductivity compared to the composite electrolytes, but at 650 ~ 800°C the 95 wt.% La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 ‐ 5 wt.% Ce 0.8 Gd 0.2 O 1.9 composite electrolyte presents the highest conductivity, reaching 0.035 S cm −1 at 800°C. The cell performances based on La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 ‐Ce 0.8 Gd 0.2 O 1.9 electrolytes were measured using Sr 2 CoMoO 6 ‐La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 as anode and Sr 2 Co 0.9 Mn 0.1 NbO 6 ‐La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 as cathode, respectively. At 800°C, the measured open‐circuit voltages are higher than 1.08 V, and the maximum power density and current density of the fuel cell prepared with 95 wt.% La 0.9 Sr 0.1  Ga 0.8 Mg 0.2 O 2.85 ‐ 5 wt.% Ce 0.8 Gd 0.2 O 1.9 electrolyte reach 192 mW cm −2 and 720 mA cm −2 , respectively.