Crystal structure and phase transition behavior of La 1- xSr xGa 1- yMg yO 3- δ

Abstract

The crystal structure and structural phase transition of La 1- x Sr x Ga 1- y Mg y O 3- δ prepared by heat treatment at 1450 °C for 24 h were evaluated by X-ray diffraction measurements, differential scanning calorimetry (DSC) and dilatometry. La 1- x Sr x GaO 3- δ with x larger than 0.05 could not be obtained as a single phase. LaGa 1- y Mg y O 3- δ with 0≤ y≤0.2 could be prepared as a single phase, although Bravais lattice varied from primitive orthorhombic to a body-centered one with substitution of y=0.1 Mg. Partial substitution of Sr for La site in LaGa 1- y Mg y O 3- δ whose y=0.15 and y=0.20 was possible with solution limit of 0.10 and 0.20, respectively. The crystal system changed from orthorhombic to cubic at Sr content of 0.15 in La 1- x Sr x Ga 0.8Mg 0.2O 3- δ . The structural phase transition to rhombohedrally distorted perovskite by temperature was observed in orthorhombic La 1- x Sr x Ga 1- y Mg y O 3- δ , whose transition temperature increased with increase of Sr and Mg content. Δ H and Δ V at the phase transition drastically decreased with increase of Mg content, which could be ascribed to smaller distortion from ideal perovskite in body-centered orthorhombic than in primitive orthorhombic.