Study of diffuse phase transition and relaxor ferroelectric behavior of Ba0.97Bi0.02Ti0.9Zr0.05Nb0.04O3 ceramic

摘要

In the present work, structural property of polycrystalline sample Ba0.97Bi0.02Ti0.9Zr0.05Nb0.04O3 (BBTZN) prepared by a molten-salt method were investigated. X-ray diffraction analyses revealed the formation of a single-phase pseudocubic structure with a Pm (3) over barm space group. Unlike the trend observed in classic ferroelectrics, the temperature dependence of the dielectric constants showed the presence of three sequences of structural phase transitions. In fact, the local disorder provides a frequency dependent relaxor like behaviours attributed to the dynamic of polar nanoregions (PNRs). The diffuse phase transition (DPT) analyzed using the modified Curie-Weiss law and Lorenz formula confirms the presence of short-range association between the nanopolar domains. The obtained values of the degree of diffuseness are found to be in the range of 1.58-1.78 due to the existence of different states of polarization and, hence, different relaxation times in different regions. The frequency dependence of temperature at dielectric maxima, which is governed by the production of PNRs at a high temperature, satisfies the Vogel-Fulcher (V-F) law. The temperature dependence of the electric modulus for various frequencies indicating a thermally activated relaxation ascribed to the Maxwell-Wagner (M-W) space charge relaxation phenomenon.