Effect of High Pressure on the Lattice Parameters of Cr2O3 and α‐Fe2O3

The effect of pressure to several hundred kilobars has been measured on Cr2O3 and α‐Fe2O3. Both have the corundum structure. Results are compared with previously published data for Al2O3.Cr2O3 exhibits a compressibility which decreases markedly with increasing pressure; Al2O3 has a compressibility nearly independent of pressure; the compressibility of α‐Fe2O3 actually increases with pressure in the low‐pressure region. This is probably associated with the unusual behavior observed in Mossbauer studies.Based on hexagonal indexing, Al2O3 shows the smallest change in aH and the largest change in CH. Cr2O3 is at the opposite extreme with α‐Fe2O3 in between. In rhombohedral indexing, Al2O3 exhibits the largest change in aR and Cr2O3 the smallest. Al2O3 shows an increase of ½ deg in α, Cr2O3 a decrease of about 1 deg, while for Fe2O3 α is nearly independent of volume.