MECHANICAL BEHAVIOR OF FERROELECTRIC CERAMICS.

Abstract

The author reviews the mechanical behavior, and in particular, the strength, fracture toughness and susceptibility to environmentally enhanced crack growth in ferroelectric materials such as barium titanate and lead zirconate titanate (PZT). Polycrystalline ferroelectric ceramics are known to exhibit a critical fracture toughness, K//I //C, as measured by classical fracture mechanics techniques, which depends strongly on grain size, and in the case of PZT, chemical composition and phase content. Mechanisms that can contribute to the crack growth resistance of ferroelectric ceramics are discussed in terms of their dependence on variables such as grain size, composition and crystal structure. It is shown that fracture toughness models can be used to predict microstructures which should lead to an optimum in crack growth resistance for a given material. The microstructure of a ferreoelectric ceramic is shown to have a direct effect on the strength of a component as well as influence its resistance to the growth of large cracks. The susceptibility of each material to environmentally enhanced fracture is shown to be particularly dependent on its chemical composition.