Phase transformation of Gd₄Al₂O₉ at high temperature

High temperature orthorhombic phase was synthesized at 1700°C for 30-50hr in air. The orthorhombic phase was possible to quench to room temperature above the critical grain size of 3μm. From the results of high temperature XRD, DSC and dilatometry analyses, phase transformation from low temperature monoclinic to high temperature monoclinic phase was observed at about 1100°C, and transition temperature at about 1400°C would correspond to the phase transformation from monoclinic to orthorhombic phase. This orthorhombic phase was transformed into low temperature monoclinic phase by polishing at room temperature.