Sintering kinetics of the α-Al_2O_3 powders with average particle size 0.1 μm and ca.1 ZrO_2 impurity was investigated. Several two-step sintering methods were tried, and the results were compared with the conventional (one-step) process. The temperature ( 98 TD) were achieved by heating to 1450℃, then holding at 1350℃ for 20 h. The sintering mechanism was determined, belonging to lattice diffusion in the temperature region of 1400 to 1600℃. The activation energy was 688 kJ/mol, which was interpreted as a volume diffusion of Al~(3+) ions in polycrystalline matrix.
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