Dielectric and impedance spectroscopy of zirconium modified (Na0.5Bi0.5)TiO3 ceramics

Abstract

Preliminary structural and detailed dielectric and electrical properties of zirconium (Zr) modified-sodium bismuth titanate (i.e., Na 0.5 Bi 0.5 Ti 1− x Zr x O 3 (NBZT)) ceramics were studied. Structural analysis of the materials with room temperature X-ray diffraction data confirmed the formation of compounds in the rhombohedral crystal system. SEM micrographs of the compounds showed the abnormal grain growth but with better densification and homogeneity on substitution of Zr at the Ti site. Dielectric and complex impedance spectroscopic studies were carried out in a wide frequency (i.e., 10 2 –10 6 Hz) and temperature (30–500 °C) range. The maximum permittivity (at transition temperature) was found to be decreased on increasing Zr concentration in NBZT but the diffuseness of dielectric peak increases. The nature of frequency dependence of ac conductivity of NBZT follows the Jonscher power law, and calculated dc conductivity follows Arrhenius behavior. Detailed studies of complex impedance spectroscopy have provided better understanding of: (i) relaxation process and (ii) microstructure-properties relationship in the materials. Complex impedance and modulus spectra confirm the significant contribution of both grain and grain boundary to electrical response of the materials. It is observed that relaxation processes in the materials are of non-Debye type.