CERAMIC COMPOSITES OF MONAZITE AND ALUMINA

A new family of high-temperature, oxidation-resistant, ceramic composi tes, with (La)-monazite (LaPO4) serving as a weakly bonded interphase, is proposed. Monazite is stable and phase-compatible with alumina at temperatures at least as high as 1750 degrees C in air. Especially imp ortant for use in high-toughness composites, the monazite-alumina inte rface is shown to be sufficiently weak that interfacial debonding prev ents cracks from growing from monazite into alumina. Observations of f racture responses of fibrous and laminar reinforcements are presented.