Sintering and Microstrusture of Al2O3 and Al2O3-ZrO2 Ceramics

Alumina powder and two commercial 3 mol% yttria-partially stabilized zirconia powders–0.3 wt% Al2O3-doped (Al-Y-PSZ) and without Al2O3 (Y-PSZ)–were used to produce alumina-zirconia (Al2O3-ZrO2) slip cast composites. The influence of the substitution of Al2O3 by 50 vol% of the different zirconia powders on the sintering kinetic at the intermediate stage was investigated. In addition, the microstructure of Al2O3 and the different composites at temperatures in the range of 1100-1600°C was studied and related to the sample hardness. An increase in the sintering rate was observed when 50 vol% Y-PSZ was substituted by 50 vol% Al-Y-PSZ. 50 vol% zirconia was effective to reduce the rate of Al2O3 grain growth in the final sintering stage. For 50 vol% Al-Y-PSZ a smaller ZrO2 grain size distribution compared with 50 vol% Y-PSZ could be achieved. As the average Al2O3 grain size of the sintered samples became greater than about 1μm a markedly decrease in the hardness was found; this occurred at temperatures higher than 1400°C, since de composites with 50 vol% zirconia reduced the rate of Al2O3 grain growth a decrease in hardness up to 1600°C was not observed.