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

Abstract

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 K_T=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 K_T of α‐Al₂O₃ and Cr₂O₃, and a value of 2.31±0.10 Mbar for K_T of α‐Fe₂O₃ in the pressure range below 30 kbar.