Ceramic Composites of Monazite and Alumina

Abstract

A new family of high‐temperature, oxidation‐resistant, ceramic composites, with (La)‐monazite (LaPO 4 ) serving as a weakly bonded interphase, is proposed. Monazite is stable and phase‐compatible with alumina at temperatures at least as high as 1750°C in air. Especially important for use in high‐toughness composites, the monazite‐alumina interface is shown to be sufficiently weak that interfacial debonding prevents cracks from growing from monazite into alumina. Observations of fracture responses of fibrous and laminar reinforcements are presented.