Microstructural changes in sintered Al2O3 by acid treatment of compacts produced by slip casting in gypsum molds

Slip casting in gypsum molds is one of the important forming methods industrially. Sintering compacts which were produced by slip casting using gypsum molds showed abnormal grain growth. The grain size of the compacts sintered at 1350 °C was in the range of 0.2–2 μm. The grain size of the compacts sintered at 1450 and 1550 °C were in excess of 2 μm and the sintered compacts showed discontinuous grain growth. Calcined bodies produced by slip casting using gypsum molds were washed with acid to remove the contamination from the bodies. The grains of these sintered compacts grew normally. The mean grain sizes were about 0.8, 5 and 8 μm respectively after sintering at 1350, 1450, and 1550 °C. The microstructure became more homogeneous. The relative densities of the sintered compacts were higher than those of the sinteried compacts. Grain-growth activation energy was calculated from experimental data. The activation energy was 4.8×103 J/mol.