Influence of small cyclic and DC electrical loads on the fracture toughness of ferroelectric ceramics

The present work investigates the influence of small AC, unipolar cyclic and DC electric loads on the fracture toughness of a ferroelectric ceramic. Single-edge-notched beams (SENB) of a poled and unpoled lead zirconate titanate (PZT) ceramic were fractured in a four-point-bending device under conditions of controlled crack growth. During crack advance the different electrical loads were applied perpendicular to the crack faces. The applied nominal electric field amplitudes were less than one third of the coercive field and maximum frequencies of 20 kHz were applied. The measured R-curves show that even for these low amplitudes, electrical AC loading causes a drop in the critical mechanical load of up to 25%. The drop increases with increasing amplitude and frequency. Possible mechanisms to explain the results are discussed.