Crystal structure and phase transition behavior of La1-xSrxGa1-yMgyO3-δ

The crystal structure and structural phase transition of La1-xSrxGa1-yMgyO3-δ prepared by heat treatment at 1450 °C for 24 h were evaluated by X-ray diffraction measurements, differential scanning calorimetry (DSC) and dilatometry. La1-xSrxGaO3-δ with x larger than 0.05 could not be obtained as a single phase. LaGa1-yMgyO3-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 LaGa1-yMgyO3-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 La1-xSrxGa0.8Mg0.2O3-δ. ructural phase transition to rhombohedrally distorted perovskite by temperature was observed in orthorhombic La1-xSrxGa1-yMgyO3-δ, whose transition temperature increased with increase of Sr and Mg content. ΔH and ΔV 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.