High-temperature impedance and alternating current conduction mechanism of Ni0.5Zn0.5WO4 micro-crystal for electrical energy storage application

Abstract

The Ni0.5Zn0.5WO4 crystals were prepared via conventional solid-state synthesis techniques, and its phase formation with monoclinic structure (space group- P2/c) was investigated with a view to understanding its structural, morphological and dielectric properties. The phase formation and average particle size (31.38 μm) were ascertained by X-ray diffractometry and field emission scanning electron microscope techniques, respectively. The real and imaginary impedance ( Z′, Z′′),dielectric constant (ɛr), loss (δ), and ac conductivity (σac) were measured in the frequency range 100 Hz-1 MHz with high-temperature evolution (200–460 °C). The grain, grain boundary and electrode ceramic effect were well fitted with R(RQ)(RQ)(RC) resistor network model using ZSimpWin software. The Non-Debye type dipolar relaxation and NTC effect were observed with high-temperature evolution above 2000c. The dielectric constant and loses were enhances with rising of temperature and ac conductivity was fitted with well-known Jonscher power law. The conduction mechanism was explained with both NSPT and CBH model from the variation of frequency exponent (n) with temperature.