Observation of crack growth in a polycrystalline ferroelectric by synchrotron X-ray diffraction.

Pre-cracked samples of unpoled, polycrystalline, soft ferroelectric lead zirconate titanate were subjected to electrical and mechanical loading whilst using synchrotron X-ray diffraction to map strain-fields. Clear evidence is found of switching around the crack tip and development of a crack-wake. A J-integral estimate based on strain-field data provided a sensitive measure of strain changes during loading. Electrical loading did not cause crack advance or crack-tip switching; this provides evidence for electrically permeable crack models. There was also enhancement of electrically-driven switching in the crack-wake region. The results provide improved understanding and a resource for testing fracture models in ferroelectrics.