Introduction

Mullite is the only stable crystalline compound in the Al₂O₃-SiO₂ system under normal atmospheric pressure. The diagram of Al₂O₃-SiO₂ is of significance to ceramic technology, being directly related to a number of ceramic materials, refractories in particular (silica, fireclay, high-alumina ceramics, sintered corundum, etc.). From the nature of phase equilibria in the Al₂O₃-SiO₂ system, it is clear that knowledge of phases in this system could be obtained for a wide variety of ceramic and glass products. For example, SiO₂ is the basis for the glass manufacturing industry whereas Al₂O₃, the other component of the phase diagram, is used in the production of electronic substrates, spark plugs, cutting tools, and lamp envelops. Mullite and many other compositions in this system are useful in various applications. During the last few decades, many research studies have been conducted on various basic topics as well as on various fields of application.