DIELECTRIC RESPONSE AND IMPEDANCE SPECTROSCOPY OF (Na0.5Bi0.5)0.95Ba0.05Zr0.04Ti0.96O3 FERROELECTRIC CERAMIC

Abstract

A new lead-free ferroelectric relaxor ceramic was prepared by conventional solid-state synthesis by modifying A-site and B-site in (Na0.5Bi0.5)TiO3 system, i.e., (Na0.5Bi0.5)0.95Ba0.05Zr0.04Ti0.96O3 (0.05BNBZT). X-ray diffraction studies reveal a single phase rhombohedral structure. Crystallite size and strain analysis has been done by Debye–Scherrer and Williamson–Hall technique. The tolerance factor is 0.81, indicating a stable Perovskite structure of the material. Scanning electron micrograph of the material shows a distribution of grains, average grain size is 1.41 μm. Dielectric response of (Na0.5Bi0.5)0.95Ba0.05 Zr0.04Ti0.96O3 , ferroelectric ceramic has been studied as a function of frequency over a wide range of temperatures. The studied ceramic exhibited maximum frequency dispersion in both real and imaginary part of dielectric susceptibility at and around the dielectric transition temperature (Tm). The frequency dependence of transition temperature, Tm (temperature of the maximum of dielectric constant) was studied in terms of Vogel–Fulcher relation. The dielectric relaxation of (Na0.5Bi0.5)0.95Ba0.05Zr0.04Ti0.96O3 ceramic was studied at different temperatures using the complex impedance (Z*) and electrical modulus (M*) formalism. Impedance measurements were made on over a wide range of temperatures (300–600°C) and frequencies (45 Hz–5 MHz) which show the presence of both grain and grain boundary effects in the material. The Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grain boundaries (at higher temperature), in addition to granular contribution (at all temperatures), which influences the device properties of a material. The electric modulus (M*) formalism used in the analysis enabled us to distinguish and separate the relaxation processes. Conductivity studies in the material obey the Jonscher's power law in frequency (45 Hz–5 MHz) and temperature (30–600°C). These results give evidence that the lead-free ferroelectric ceramics is extensively may be used for device and electronic applications, when compared with lead-based materials.