Influence of Electric Field and Mechanical Stresses on the Fracture of Ferroelectrics

This chapter reviews experimental results that allow one to interpret the essential features of fracture in ferroelectric ceramics under electric and mechanical load. First, crack growth measurements on unpoled and poled ferroelectric ceramics are reviewed, and numerous experiments that demonstrate the existence and relevance of a domain-switching zone are presented. Thereafter the review concentrates on results of fracture experiments with applied electric fields and addresses the controversial outcomes of such experiments. Theoretical fracture mechanical concepts are then introduced. One part of the discussion focuses on electrical boundary conditions used at the crack surface because they decisively determine the predicted energy release rate. The other part of the discussion, which concerns theoretical concepts, discusses the predicted switching zones around cracks and their influence on the stress intensity factor and energy release rate. Finally, this chapter attempts to mirror the tremendous theoretical framework against the existing experimental results and critically review the relevance of the developed fracture mechanics concepts of piezoelectric ceramics.