HOT-PRESSING OF CR2O3 POWDER WITH THIN HEXAGONAL PLATE PARTICLES

Chromium oxide (Cr2O3) powders with thin hexagonal plate particles hav e been obtained at 1200 degrees C to 1400 degrees C from an amorphous material prepared by adding hydrazine monohydrate to the aqueous solut ion of chromium nitrate. Tablets molded by wet-uniaxial-pressing were hot-pressed for 2 h at 1500 degrees C and 30 MPa. The dense sintered C r2O3 ceramics (>98% of theoretical) obtained had crystal-orientation, in which a < 001 > axis was parallel to the pressing direction. They e xhibited an anisotropy in electrical conductivity, s; the values measu red at 700 degrees C in the perpendicular and parallel directions for the < 001 > axis were 5.5 and 0.58 S . m(-1), respectively. Vickers ha rdness, HV,and fracture toughness, KIC, were 24.1 GPa and 4.6 MPa . m( 1/2), respectively.