INTELLIGENT CERAMIC MATERIALS - ISSUES OF BRITTLE-FRACTURE

In this paper we review the brittle fracture behavior of piezoelectric and electrostrictive ceramics of interest for intelligent material systems. Properties of importance, such as critical fracture toughness, strength, and susceptibility to moisture enhanced crack growth, are addressed, especially as they are affected by the material's microstructure and chemistry. Local strains and ferroelectric domains produced by phase transformations in these materials are shown to have a direct influence on both fracture toughness and strength. The cyclic stressing of a piezoelectric ceramic is discussed in terms of the structural damage produced by this mode of loading. Finally, tradeoffs in improved reliability, which may be achievable through suitable variations in composition or microstructure, are compared against possible losses in the piezoelectric properties of interest.