High-pressure x-ray diffraction and Raman spectra study of indium oxide

High-pressure synchrotron radiation x-ray diffraction and Raman spectroscopy measurements of indium oxide $(In2O3)$ were carried out at room temperature up to 27.8 and 26.2 GPa, respectively. A pressure-induced phase transition from cubic-phase $(Ia3¯)$ was observed at a pressure above 12.8–15.3 GPa, which disagrees with earlier theoretical prediction (3.8 GPa). According to the x-ray diffraction experimental data, the high-pressure phase is isostructural with hexagonal corundum-type structure (⁠$R3¯c$ symmetry). However, broad peaks observed in Raman spectra suggest that the high-pressure structure is disordered. The volume change from cubic phase to corundum phase is about 4% and the axial ratio $c/a$ in the corundum phase decreases with increasing pressure.