The effects of ternary compound additives, MnO2-TiO2-CAS (CaO-Al2O3-SiO2glass) and MgO-Y2O3-SiO2on the densification and microstructure of alumina have been investigated, using simplex design and regression analysis. The results show that the enhanced densifications can be achieved by co-doping due to the combined effects of compound additives. With the addition of MnO2, TiO2, and CAS fixed at 0.6 wt% of the total weight of the ceramic and in the proportion of 2:3:1, the sample sintered at 1550 °C for 1 h reaches about 97% of theoretical density. Approximately 98% of theoretical density can be obtained for the sample incorporating the MgO-Y2O3-SiO2additives, when the addition of MgO, Y2O3, and SiO2was fixed at 6 wt% of total weight of the ceramic and in the proportion of 1:3:2. The influence of proportions of MnO2, TiO2, and CAS as well as MgO, Y2O3, and SiO2on the anisotropic and abnormal grain growth, and grain size are also discussed. © 2007.
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