Role of sintering temperature on microstructure and nonlinear electrical properties of 0.1 mol.% Nb_2O_5 added ZnO-V_2O_5 varistor ceramics

摘要

The effect of sintering temperature on the microstructure, density and nonlinear electrical properties of 0.1mol% Nb2O5 added ZnO-V2O5 varistor ceramics had been investigated. Density measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD) pattern analysis characterized the sintered samples. The electric current and capacitance measurements of the varistor samples were done in varying voltage over a wide range. Image analysis by SEM shows an increase in the average grain size from 2.8 to 7.2 mu m when the sintering temperature increases from 850 to 975 degrees C. The varistor sample, sintered at 850 degrees C, exhibits breakdown field of 4258V/cm with nonlinear exponent value of 24. Degradation in breakdown field (1440V/cm) and nonlinear exponent (9) have been observed with an increase in sintering temperature up to 975 degrees C. Barrier height estimated from the electric field-current density (E-J) and the capacitance-voltage (C-V) measurements follow an inverse relationship with sintering temperature.