Role of sintering temperature on microstructure and nonlinear electrical properties of 0.1 mol.% Nb2O5 added ZnO–V2O5 varistor ceramics
The effect of sintering temperature on the microstructure, density and nonlinear electrical properties of 0.1 mol% 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 µm when the sintering temperature increases from 850 to 975 °C. The varistor sample, sintered at 850 °C, exhibits breakdown field of 4258 V/cm with nonlinear exponent value of 24. Degradation in breakdown field (1440 V/cm) and nonlinear exponent (9) have been observed with an increase in sintering temperature up to 975 °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.
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