Effects of Ground Alumina Powder on Platelike Grain Growth

Abstract

Trace amounts of impurities in alumina powder are known to cause platelike alumina grains to generate in sintered bodies. In many studies of platelike alumina grain growth in sintered bodies, fine and high pure alumina powders built-up by the sol-gel method have been examined by addition of SiO2, CaO and so on. The authors reported in a previous paper that the platelike grains were formed in sintered compacts of a fine alumina powder ground by wet rotation ball milling. In this study, sintering properties were investigated for two kinds of alumina powders: ground powder, built-up powder with similarities in average particle size, particle mass-size distribution and amounts of impurities. The platelike grains were generated in both of powder compacts. However, platelike grains of ground powder compacts were formed at low sintering temperatures and short sintering time compared to other compacts, which can be explained by the fact that the ground powder contained ultra-fine particle of less than or equal to 0.1μm. The grinding processes proceeded with micro-decay of particle surface on the powder. When platelike grain growth isotherms in logarithmic plot were compared, the slopes were nearly equivalent. Therefore, it was suggested that the platelike grain growth mechanism of two kinds of powders compacts was similar.