HIGH-PRESSURE SINTERING OF MICROCRYSTALLINE AND HIGHLY PURIFIED ALUMINA CERAMIC

Pure Al2O3 ceramic and MgO-doped Al2O3 ceramic were prepared by high-pressure sintering, using a commercially avail-able alpha-alumina nanopowder with a purity of 99.9% in mass and Mg(NO3)2 (analytical reagent) as the starting materials. These ceramics were characterized by density measurement and microstructure analysis. The sintering temperature of the highly purified Al2O3 ceramic decreases remarkably in the high-pressure sintering, as compared with the normal-pressure sintering, and the velocity of mass transfer also enhances, which shortens the sintering time. The high-pressure sintering can achieve fast-and low-temperature sintering. MgO has no effect on the densification of the highly purified Al2O3 ceramic in the high-pressure sintering process, which is obviously different than that in the normal sintering. The pure Al2O3 ceramic, with a relative density of 97.65%, and MgO-doped Al2O3 ceramic, with a relative density of 97.93% and an average grain size of 4 μm, were obtained by sintering for 30 minutes under a pressure of 4.5 GPa and a temperature as low as 1 100 ℃ .