Direction of Liquid Film Migration Induced by Chromic Oxide in Alumina-Anorthite

Abstract

Three kinds of single-crystalline alumina plates with the crystallographic planes of C, m, and R were diffusion-bonded with liquid-phase sintered (98)alumina-(2)anorthite (in wt%) plates (P) and then heat-treated at 1600 degrees C under a Cr2O3-containing atmosphere, During the heat treatment, for all of the specimens studied, the anorthite liquid films between alumina plates migrated to grains with surface orientation corresponding to higher coherency strain energy, This result is in better agreement with a prediction based on the coherency strain theory than the previous one obtained for grain-boundary migration, The discrepancy between the predicted and previously observed migration directions of some grain boundaries in alumina may therefore be attributed to an effect of grain-boundary structure and stress transmission across the boundary.