Abstract: The polycrystal ceramics with the content of alumina more than 99.5wt; were prepared by sintering at low temperature with rare earth oxide Y2O3 and Tm2O3 as sintering aids. Addition of Y2O3 and Tm2O3 in the alumina powders decreased the sintering temperature and improved the relative density effectively. Compared to monolithic alumina ceramics and alumina ceramics with single rare earth oxide addition,the mixture, Y2O3 + Tm2O3, can restrain the growth of grains, and make the size of grains uniform, and finally form a compact structure. The trans-granular fracture is the main fracture mode for the polycrystal alumina ceramics with Y2O3 + Tm2O3. The size of grains is from 3 to 5μm, and the maximum bending strength is 533MPa, hardness is 17.2GPa.

Key words: The polycrystal ceramics with the content of alumina more than 99.5wt; were prepared by sintering at low temperature with rare earth oxide Y2O3 and Tm2O3 as sintering aids. Addition of Y2O3 and Tm2O3 in the alumina powders decreased the sintering temperature and improved the relative density effectively. Compared to monolithic alumina ceramics and alumina ceramics with single rare earth oxide addition,the mixture, Y2O3 + Tm2O3, can restrain the growth of grains, and make the size of grains uniform, and finally form a compact structure. The trans-granular fracture is the main fracture mode for the polycrystal alumina ceramics with Y2O3 + Tm2O3. The size of grains is from 3 to 5μm, and the maximum bending strength is 533MPa, hardness is 17.2GPa.