Abstract
Pressure-induced phase transition in the technologically important tetragonal phase of has been quite controversial with two entirely different propositions: (1) morphotropic phase boundary-like structural transition with concomitant rotation of the ferroelectric polarization vector and (2) antiferrodistortive (AFD) phase transition followed by emergence of a reentrant ferroelectric phase. We have attempted to address these controversies by enhancing the AFD instability of through 50% substitution in a tetragonal composition of the solid solution system. Using a high resolution synchrotron x-ray diffraction study of the pressure-induced phase transition in this composition, we present here experimental evidence for the emergence of superlattice reflections at a moderate pressure due to an AFD transition leading to a monoclinic phase in the Cc space group, which permits the rotation of the ferroelectric polarization vector. We also present evidence for a reentrant ferroelectric phase above in which octahedral tilting provides an efficient mechanism for accommodating volume reduction. The implications of these findings in resolving the existing controversies in and in providing insight for designing environmentally friendly Pb-free piezoelectric compositions are also discussed.
1 More- Received 12 March 2019
- Revised 30 May 2019
DOI:https://doi.org/10.1103/PhysRevMaterials.3.094405
©2019 American Physical Society