Relaxation and Conduction Mechanisms of High Tc Lead-Free Ba (Zr,Ti)O3 Positive Temperature Coefficient of Resistivity Ceramic Using Impedance Spectroscopy

Abstract

High Tc lead–free Ba (Zr0.52Ti0.48)O3 positive temperature coefficient of resistivity (PTCR) ceramic was produced by the standard solid state reaction technique. X–ray diffraction pattern confirms the formation of the tetragonal perovskite structure of the ferroelectric sample. The conduction and relaxation mechanisms of the piezoelectric ceramic have been studied on the basis of activation energy. The relaxation mechanism is investigated for this sample based on the peaks of the imaginary part of electrical impedance and modulus spectra. The Cole-Cole plots indicate that the grain effect is influenced by the increase of temperature up to 200 °C and disappeared beyond this temperature. The temperature versus electrical resistivity plots show that a phase transition occurs at the Curie temperature, Tc =150 °C. The ceramic exhibits a PTCR jump of almost two orders of magnitude starting at 150 °C and ending at 275 °C with a high temperature coefficient of resistivity of ~25 % per °C. The electrical resistivity measurements also reveal that the sample shows semiconducting behavior beyond 275 °C with the value of negative temperature coefficient of resistivity of ~ 0.6% per °C.