In situ observation of electric-field-induced domain switching and crack propagation in poled PMNT62/38 single crystals

It is important to in situ observe the crack propagation and the corresponding domain switching in ferroelectrics subjected to electric loading since domain switching has been widely assumed to play a critical role in the electric-field-induced crack growth. In this investigation, we in situ observed the crack propagation and the domain switching in PMNT62/38 single crystals poled along the [001] orientation. An experimental setup was designed and constructed to investigate the crack propagation and the domain switching in thin plate specimens with pre-crack subjected to electric field by using polarized light microscope (PLM). The pre-crack began to propagate forward accompanied by the appearance of domain switching zones near the crack tip and the disappearance of switched zones behind the crack tip at the unipolar electric field of E = 0.8E_C. The results indicate that the structure mismatch of the adjacent switched zones with different polarizations stimulated by the intensive electric field near the crack tip results in the electric-field-induced crack growth.