Abstract
Lead titanate (PbTiO3) is a classical example of a ferroelectric perovskite oxide illustrating a displacive phase transition accompanied by softening of a symmetry-breaking mode. The underlying assumption justifying the soft-mode theory is that the crystal is macroscopically sufficiently uniform that a meaningful free energy function can be formed. In contrast to PbTiO 3, 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 PbTiO 3, 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.
| Original language | English |
|---|---|
| Article number | 174104 |
| Journal | Journal of Applied Physics |
| Volume | 113 |
| Issue number | 17 |
| DOIs | |
| State | Published - May 7 2013 |
Funding
Raman measurements were conducted at the Center for Nanophase Materials Sciences, sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The work at Simon Fraser University was supported by the U.S. Office of Naval Research (N00014-11-1-0552 and N00014-12-1-1045) and the Natural Science and Engineering Research Council of Canada. The authors thank Dr. C. M. Rouleau for assistance with the Raman measurements. The research work was supported by the collaboration project between the Center of Excellence for Advanced Materials Research at King Abdulaziz University in Saudi Arabia (Project No. T-001/431) and the Aalto University.