Enhancement of electrical energy storage ability by controlling grain size of polycrystalline BaNb2O6 for high density capacitor application

Abstract

The present article focuses on the electrical energy storage capacity of BaNb2O6 (BN) ceramic material with varying sintering time duration of material synthesized by solid state reaction method. The crystal phase formation during calcination process was studied with high temperature x-ray diffraction, which confirms the formation of desired crystalline phase at temperature above 1100 °C. The associated micro-structural images reveal increasing trend of average grain size from 4.32 μm to 10.08 μm with raising sintering time. A decrease in Z′ with temperature confirms the occurrence of negative temperature coefficient (NTCR) behavior of BN ceramic similar to semiconductor material. The impedance spectroscopy provides the electrical equivalent circuit of investigated BN ceramic. Fitting of these data with three R and Q (CPE) elements connected in series revealed an important information regarding grain, grain boundary and electrode effects. The frequency dependent conductivity of the material follows the Jonscher’s power law and found increase in frequency exponent n from 0.51 to 0.92 for BN05 to BN50 that suggests shifting of ionic long-range translational motion to localized motion of ions/charge carriers. The activation energy, calculated from curve between relaxation time and inverse temperature, reduces from 0.59 eV to 0.33 eV for sample BN05 to BN50. The recoverable energy increases from 2.12 to 10.28 mJ/cm3 with sintering time interval whereas, the storage energy efficiency enhanced from 12.98% to 57.85%.