Thermal and laser irradiation effects on dielectric properties of zinc ferrite

Abstract

Spinel zinc ferrite (ZF) nanomaterial was synthesized by using sol–gel auto-combustion route. Resulted ZF nanomaterial was characterised by synchrotron x-ray diffraction (S-XRD), energy dispersive x-ray (EDX) and field emission scanning electron microscope (FE-SEM). S-XRD pattern confirms the ‘F-d3m space group’ cubical spinel structure, EDX reveals the composition and FE-SEM gives morphological properties. ZF in the form of pellet was irradiated by pulsed Nd:YAG laser with 1.2 W power and λ = 1064 nm. Dielectric constants (ε’ & ε”) and dielectric loss (tanδ) have been plotted with frequency at different temperatures ranging from 303 K to 750 K. Dielectric constants decreased with the increase in frequency as the exchange of electrons among Fe3+↔Fe2+ does not follow the frequency of applied alternating field beyond certain frequency. Decrement in tanδ is more prominent for irradiated pallet at low frequencies while it becomes nearly equitable at high frequencies. AC conductivity (σac) increases with the increase in temperature exhibiting the semiconducting behavior. Measured σac was fitted with Jonscher power law and DC conductivity (σdc) was extracted from the fitting at different temperatures ranging from 303 K to 750 K. Activation energy (E), calculated from ln σdc versus 1000/T plots increased slightly for ZF-2 than that of ZF-1. The changes in dielectric properties occur because of electrons hopping among Fe2+ and Fe3+ and oxidation states due to thermal treatment and laser irradiation.