Pre-existing cracks, introduced by a Vickers diamond hardness indenter in BM500 (Navy Type II) PZT, exhibit visible
growth and thickening when subjected to low frequency electric fields with amplitudes above a threshold on the order of
1.66 E<sub>c</sub>. Thickening, but no growth, of cracks is also observed after cycles of a field of 1.64 E<sub>c</sub>. The threshold field is
related to the ferroelectric, piezoelectric and elastic properties of the ceramic. At fields above the threshold, cracks grow
to a limiting size after a relatively low number of cycles, and then increase in width, as opposed to length, when further
electric cycles are applied. The maximum size to which field-induced cracks grow is of the order of the separation of the
electrodes. Changes observed in the resonance peaks of impedance spectra may be used as a basis for non-destructive
identification of defects in piezoelectrics.
Pre-existing cracks introduced by a Vickers diamond hardness indenter in PMN-0.3PT, which displays piezoelectric properties, increase in length under the action of low frequency cyclic electric fields applied normal to the crack. A minimum applied field of 1.1 x Ec is required to cause crack growth. In applied fields of 1.85-5.70 x Ec cracks grow to a common limiting length which is approximately 0.8 times the separation between the electrodes. New cracks are not generated at the corners of a Vickers diamond indent by applied fields up to 5.70 x Ec.