Hot pressing of Cr2O3 powder with thin hexagonal plate particles

Chromium oxide (Cr2O3) powders with thin hexagonal plate particles have been obtained at 1200°C to 1400°C from an amorphous material prepared by adding hydrazine monohydrate to the aqueous solution of chromium nitrate. Tablets molded by wet-uniaxial-pressing were hot-pressed for 2 h at 1500°C and 30 MPa. The dense sintered Cr2O3 ceramics (>98% of theoretical) obtained had crystal-orientation, in which a 〈001〉 axis was parallel to the pressing direction. They exhibited an anisotropy in electrical conductivity, s; the values measured at 700°C in the perpendicular and parallel directions for the 〈001〉 axis were 5.5 and 0.58 S·m−1, respectively. Vickers hardness, HV, and fracture toughness, KIC, were 24.1 GPa and 4.6 MPa·m12, respectively.