  The contributory mechanisms associated with high piezoelectric response in
piezoelectric ceramics have been examined by in-situ electric field dependent
high energy synchro x-ray diffraction study. A comparative study of electric
field induced lattice strain and the propensity for non-180o domain switching
on two closeby compositions of a high performance piezoelectric alloy
(1-x)PbTiO3-(x)BiScO3, one within the morphotropic phase boundary (MPB) region
exhibiting d33 of 425 pC/N and another just outside the MPB region exhibiting
d33 of 260 pC/N, unravelled that, inspite of the MPB specimen exhibiting
considerably high piezoelectric response, its lattice strain and domain
switching propensity is considerably less as compared to the non-MPB specimen.
These new experimental observations contradict the commonly held view that
anomalous piezoelectric response in MPB based piezoelectrics arise due to
enhanced propensity for domain switching. Our results show the dominant
mechanism contributing to the anomalous piezo-response is field induced
interferroelectric transformation.
