Anomalous reduction in domain wall displacement at the morphotropic phase boundary of the piezoelectric alloy systemPbTiO3−BiScO3

A comparative study of field-induced domain switching and lattice strain was carried out by in situ electric-field-dependent high-energy synchrotron x-ray diffraction on a morphotropic phase boundary (MPB) and a near-MPB rhombohedral/pseudomonoclinic composition of a high-performance piezoelectric alloy $(1\ensuremath{-}x)\mathrm{PbTi}{\mathrm{O}}₃\ensuremath{-}(x)\mathrm{BiSc}{\mathrm{O}}₃$. It is demonstrated that the MPB composition showing large ${d}₃₃\ensuremath{\sim}425\phantom{\rule{0.16em}{0ex}}pC/N$ exhibits significantly reduced propensity of field-induced domain switching as compared to the non-MPB rhombohedral composition $({d}₃₃\ensuremath{\sim}260\phantom{\rule{0.16em}{0ex}}pC/N)$. These experimental observations contradict the basic premise of the martensitic-theory-based explanation which emphasizes on enhanced domain wall motion as the primary factor for the anomalous piezoelectric response in MPB piezoelectrics. Our results favor field-induced structural transformation to be the primary mechanism contributing to the large piezoresponse of the critical MPB composition of this system.