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arXiv · 1302.1606

A statistical model approximation for perovskite solid-solutions: a Raman study of lead-zirconate-titanate single crystal

J. Frantti·Y. Fujioka·A. Puretzky·Y. Xie·Z. -G. Ye·A. M. Glazer
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Abstract

Lead titanate (PbTiO3) is a classical example of a ferroelectric perovskite oxide illustrating a displacive phase transition accompanied by a softening of a symmetry-breaking mode. The underlying assumption justifying the soft-mode theory is that the crystal is macroscopically sufficiently uniform so that a meaningful free energy function can be formed. In contrast to PbTiO3, experimental studies show that the phase transition behaviour of lead-zirconate-titanate solid solution (PZT) is far more subtle. Most of the studies on the PZT system have been dedicated to ceramic or powder samples, in which case an unambiguous soft-mode study is not possible, as modes with different symmetries appear together. Our Raman scattering study on titanium-rich PZT single crystal shows that the phase transitions in PZT cannot be described by a simple soft-mode theory. In strong contrast to PbTiO3, splitting of transverse E-symmetry modes reveals that there are different locally-ordered regions. The role of crystal defects, random distribution of Ti and Zr at the B-cation site and Pb ions shifted away from their ideal positions, dictates the phase transition mechanism. A statistical model explaining the observed peak splitting and phase transformation to a complex state with spatially varying local order in the vicinity of the morphotropic phase boundary is given.

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J. Frantti, Y. Fujioka, A. Puretzky, Y. Xie, Z. -G. Ye, A. M. Glazer. 2013-02-06. A statistical model approximation for perovskite solid-solutions: a Raman study of lead-zirconate-titanate single crystal. https://doi.org/10.1063/1.4798391

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