Abstract
Effect of addition of MgO on growth behavior of platelike grains in alumina sintered bodies was investigated and also their mechanical properties were investigated. The growth of platelike grains in the direction of long axis were restrained by addition of MgO, so the aspect ratio of the grains decreased with increasing amount of MgO. However, platelike grain growth mechanism with any amount of MgO up to 0.1mass% was considered to be similar, because the slopes of growth isotherms in log-log plot of platelike grain size of long axis versus sintering time were nearly equivalent. Although the bending strength of alumina sintered bodies with 20-30vol% platelike grains was almost. the same in comparison with the bodies which did not contain platelike grains, the fracture toughness of the former bodies were about 10-40% larger than the latter bodies. The mechanism of increasing fracture toughness in this study was considered to be the crack deflection process. The fracture toughness increased with aspect ratio of platelike grains in sintered bodies.
