Rare earths in ceramic materials technology

Abstract

Rare earth elements are mainly exploited for electronic devices, but far from negligible is their importance in materials for structural applications, i.e. for their mechanical properties, useful in modern technologies. For example, widely renown is the role of rare earth oxides in the study of zirconia (zirconium dioxide, ZrO 2), by far the most interesting ceramic material for structural applications. Among rare earth oxides, ceria (cerium dioxide, CeO 2) has played a fundamental role because at room temperature it stabilizes the tetragonal phase of zirconia, which is the most interesting phase from a mechanical point of view. In this presentation the main characteristics of the system CeO 2-ZrO 2 are outlined, along with the mechanical properties of binary alloys of the two oxides; these properties are evaluated as a function of their composition and microstructure. Some of these alloys exhibited behaviour completely unexpected for ceramic materials, e.g. the Shape Memory Effect (SME) and the Gorsky Effect.