Polarization behavior in a compositionally graded relaxor–ferroelectric crystal visualized by angle-resolved polarized Raman mapping

Abstract

Explaining the properties and functions of materials in terms of their atomic arrangements and inhomogeneous structures is a fundamental challenge for the development of ferroelectric oxides. Dielectric response, a fundamental property of matter, can be explained by long-wavelength polar lattice vibrations and dipole relaxations capable of responding to electrical bias; therefore spectroscopic methods, such as Raman spectroscopy, can be used to investigate its origin. Herein, we used angle-resolved polarized Raman mapping to investigate how phase boundaries and giant dielectric responses are related in a relaxor-Pb(Mg1/3Nb2/3)O3–ferroelectric-PbTiO3 (PMN-xPT) solid-solution system using a compositionally graded crystal, with gradual changes in polarization direction visualized by Raman mapping. The variation of the width of quasielastic light scattering with position reveals the following: The huge dielectric response observed in PMN-xPT is ascribable to the slowing down of a relaxation related to mesoscopic ferroelectric domains near the phase boundary, which is characteristic of relaxor–ferroelectric solid-solution systems and differentiates them from other ferroelectrics.

Temperature-gradient investigation of phase transitions in ferroelectrics using cooling and heating stage

“…Raman scattering data were acquired using our system, which comprises a polarization rotation system installed in a microscope. 25,[28][29][30][31][32] A BaTiO 3 crystal was placed in the cooling and heating stage (with a quartz glass window) on an XYZ mapping stage installed in the microscope. Using a 10x objective lens, the focus was about 10 μm in diameter on the sample.…”

“…Therefore, we have focused on graded samples, which allow continuous variation of a physical quantity under the same experimental conditions. [25][26][27] In our investigation using a compositionally graded relaxor Pb(Mg 1/3 Nb 2/3 )O 3 and ferroelectric PbTiO 3 crystal, we have employed synchrotron X-ray diffraction (XRD) mapping and angle-resolved polarized Raman mapping to examine the structure and lattice dynamics as the composition is continuously varied, revealing that "the dielectric constant exhibits a maximum in the relaxor-rich concentration regime near MPB, attributed to the critical slowing down of polar relaxation in nanodomains." 25) While compositionally graded samples correspond to a detailed exploration of the concentration-temperature phase diagram in the horizontal direction, the introduction of a temperature gradient to the samples would enable a thorough investigation of the phase diagram in the vertical direction.…”