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arXiv · 1202.2883

High-pressure neutron study of the morphotropic PZT: phase transitions in a two-phase system

J. Frantti·Y. Fujioka·J. Zhang·S. Wang·S. C. Vogel·R. M. Nieminen·A. M. Asiri·Y. Zhao·A. Y. Obaid
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Abstract

In piezoelectric ceramics the changes in the phase stabilities versus stress and temperature in the vicinity of the phase boundary play a central role. The present study was dedicated to the classical piezoelectric, lead-zirconate-titanate (PZT) ceramic with composition Pb(Zr$_{0.54}$Ti$_{0.46}$)O$_3$ at the Zr-rich side of the morphotropic phase boundary at which both intrinsic and extrinsic contributions to piezoelectricity are significant. The pressure-induced changes in this two-phase (rhombohedral $R3c$+monoclinic $Cm$ at room temperature and $R3c+P4mm$ above 1 GPa pressures) system were studied by high-pressure neutron powder diffraction technique. The experiments show that applying pressure favors the $R3c$ phase, whereas the $Cm$ phase transforms continuously to the $P4mm$, which is favored at elevated temperatures due to the competing entropy term. The $Cm\rightarrow R3c$ phase transformation is discontinuous. The transformation contributes to the extrinsic piezoelectricity. An important contribution to the intrinsic piezoelectricity was revealed: a large displacement of the $B$ cations (Zr and Ti) with respect to the oxygen anions is induced by pressure. Above 600 K a phase transition to a cubic phase took place. Balance between the competing terms dictates the curvature of the phase boundary. After high-pressure experiments the amount of rhombohedral phase was larger than initially, suggesting that on the Zr-rich side of the phase boundary the monoclinic phase is metastable.

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J. Frantti, Y. Fujioka, J. Zhang, S. Wang, S. C. Vogel, R. M. Nieminen, A. M. Asiri, Y. Zhao, A. Y. Obaid. 2012-02-13. High-pressure neutron study of the morphotropic PZT: phase transitions in a two-phase system. https://doi.org/10.1063/1.4733570

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