Phase Relations and Transformations in Advanced Ceramic Materials

摘要

This article reviews the phase diagrams contributing to the understanding of compound formations, phase transformations, phase separation and microstructural development in advanced ceramic systems. Phase equilibrium relations in the Al_2O_3-AlN and AlN-B_2O_3 systems are presented for the fabrication of translucent aluminum oxynitride spinel ceramics and in-situ hexagonal boron nitride composites. In oxide systems, especially in glass-forming systems, crystallized phases vary with not only composition and temperature but also time of heat-treatment. Considering this aspect, time-temperature-transformation (TTT) diagrams in the solidification processes of cordierite, high-T_c superconducting oxide and fluorphlogopite melts and the phase transformations of ammonium aluminum carbonate hydroxide to α-alumina are introduced and specific phase transformations in these systems are also discussed. The effect of treatment atmosphere on microstructure in phase transformations is described in the surface-treatment of AlN ceramics and the sintering of transparent silica glass.