Thermal evolution of polar nanoregions identified by the relaxation time of electric modulus in the Bi_1/2Na_1/2TiO₃ system

¹ Key Laboratory of Nonferrous Materials and New Processing Technology, Ministry of Education, College of Materials Science and Engineering, Guilin University of Technology - Guilin 541004, China
² Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM) - Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
³ School of Physical Science & Technology and Guangxi Key Laboratory for Relativistic Astrophysics, Guangxi University - Nanning 530004, China
⁴ UNSW Australia, School of Materials Science and Engineering - 2052 Sydney, Australia

^(a) ljliu2@163.com

Received: 14 June 2017
Accepted: 3 July 2017

Abstract

The correspondence between the temperature dependence of phase structures and the experimental physical properties was made clear for the first time in the Bi_1/2Na_1/2TiO₃ system according to in situ XRD, in situ Raman and impedance spectroscopy. XRD profiles show pseudo-cubic symmetry independent of temperature, while one of the Raman models disappears near 620 K, indicating that the local symmetry increases. The temperature dependence of the main relaxation time of the electric modulus spectra can be divided into four regions, characterizing the thermal evolution of polar nanoregions (PNRs) with different symmetries and a phase transition between rhombohedral and tetragonal symmetry. Therefore, the relaxation times of the electric modulus provide a way to estimate the local phase transition and the thermal evolution of R3c and P4bm PNRs.