Fracture behavior of ferroelectric ceramics

Piezoelectric actuators are key components in many smart structures applications. Long term reliability of these actuators becomes increasingly important as research makes the transition to commercial applications. Fracture toughness is a material parameter that measures a material's resistance to crack propagation. This is, perhaps, one of the most important parameters for reliable device design. This paper reviews recent work by the authors on fracture behavior of ferroelectric ceramics. Vickers indentation data were used to determine the fracture toughness of a coarse and a fine grained PZT and two compositions of PLZT. R-curve data were obtained for two compositions of PLZT. The R-curve data presented here were generated using four point bend specimens with controlled surface flaws. The R-curve results compare favorably with the Vickers indentation data. A comparison of the R-curves for a ferroelectric composition of PLZT and a quadratic electrostrictive compositioin of PLZT demonstrate the contribution of domain reorientation to the toughening process.