William G. Fahrenholtz

Abstract Clays are ubiquitous constituents of the Earth’s crust that serve as raw materials for traditional ceramics. Mineralogically, clays are phyllosilicates or layered aluminosili­cates. Bonding is strong within layers, but weak between layers, allowing clays to break into micrometer-sized particles. When mixed with water, clays develop plasticity and can be shaped easily and reproducibly. When heated, clays undergo a series of reactions that ultimately produce crystalline mullite and a silica-rich amorphous phase. Beyond the structure and properties of clays, the science that developed to understand traditional ceramics continues to serve as the framework for the study of advanced ceramics.