Properties and microstructural analysis of La1−xSrxGa1−yMgyO3−δ solid electrolyte ceramic

Abstract La 1− x Sr x Ga 1− y Mg y O 3− δ ( x =0.1–0.2, y =0.1–0.2) (LSGM) electrolytes, which have high ionic conductivities, were synthesized by a solid-state reaction at 1500 °C. In our study, La 0.9 Sr 0.1 Ga 0.9 Mg 0.1 O 3− δ and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ crystallized in an orthorhombic ( Imma ) structure, and La 1− x Sr x Ga 1− y Mg y O 3− δ (0.1 x ≤0.2, 0.17≤ y ≤0.2) crystallized in a rhombohedral ( R 3 c ) structure. Active Raman bands at approximately 532, 674, and 750 cm −1 were observed in these samples because of the decrease in local symmetry induced by the oxygen vacancies. When x + y >0.35, the conductivity was approximately 0.164–0.173 S/cm at 800 °C. The ionic conductivity mechanism changed at temperatures of approximately 500–650 °C. La 0.9 Sr 0.1 Ga 0.9 Mg 0.1 O 3− δ and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ samples possessed higher resistances at 300–400 °C as a result of existing stacking faults and defects. The thermal expansion coefficients (TECs) were approximately 9.1×10 −6 /°C to 11×10 −6 /°C at 200–500 °C.