Hydrostatic compression of four corundum-type compounds: α-Al2O3, V2O3, Cr2O3, and α-Fe2O3

Accurate x-ray diffraction experiments for hydrostatic compression of corundum α-Al2O3 and transition-metal sesquioxides with the corundum structure, V2O3, Cr2O3, and α-Fe2O3, were performed using a cubic-anvil type of high-pressure apparatus at room temperature up to about 120 kbar. An isotropic compression of the unit cell was found in α-Al2O3 and Cr2O3. In V2O3 and α-Fe2O3, anisotropic behaviors of compression were observed: The ratio c/a in the hexagonal cell increases in V2O3 and decreases in α-Fe2O3 with increasing pressure. The isothermal bulk modulus KT=1.75±0.03 Mbar of V2O3 is unusually small among the studied compounds with the corundum structure. Values of 2.39±0.04 Mbar and 2.31±0.05 Mbar were calculated for KT of α-Al2O3 and Cr2O3, and a value of 2.31±0.10 Mbar for KT of α-Fe2O3 in the pressure range below 30 kbar.