Effect of thermal calcination on the structural, dielectric and magnetic properties of (ZnO–Ni) semiconductor

We report the variations in structural, dielectric and magnetic properties with elevation of calcination temperature of (ZnO, Ni), synthesized by hydrothermal route. Incorporation of Ni in ZnO lattice is accompanied by numerous oxygen vacancies. With increasing calcinations temperature, enhancement in particle size with improvement in crystallization are observed, which is most probably due to grain growth having less number of grain boundaries and enhancement in grain volume. The dielectric behavior gives deep insight of (ZnO, Ni) nanoparticles microstructure. The abrupt increase in A.C. conductivity (σ_a.c) at high frequencies arises due to the addition of detached charge carrier from trap states to the conduction charge carriers. The (ZnO, Ni) nanoparticles, calcined at different temperatures, show significant changes in the hysteresis loop of ZnO nanoparticles: the loop shows strong ferromagnetic (FM) behavior. The magnetization enhances with increasing the calcination temperature of the particle (Ni, ZnO). Defects (oxygen vacancies) are found to be the main reason for room-temperature ferromagnetism (RTFM) in the (ZnO, Ni) nanoparticles. The enhanced dielectric and magnetic properties of (ZnO, Ni) nanoparticles are strongly correlated with the increase of oxygen vacancies.