Effect of Annealing Temperature on Microstructural, Optical and Magnetic Properties of spinel-ZnFe2O4 Nano Particles

In this work, zinc ferrite nano-particles (ZF NPs) were synthesized using co-precipitation method and annealed at different temperatures 400, 600 and 800 °C in air ambient. It is observed that temperature significantly effects the structural, optical and magnetic properties of ZF NPs. The high-resolution X-ray diffraction (HR-XRD) spectra of ZF NPs is matched with JCPDS card No. 00–022-1012, which shows a single-phase cubic spinel structure with Fd-3 m space group. The estimated average crystallite size is in the range of 11.8–18.4 nm. The scanning electron microscope images shows that the particle size of ZF NPs is increased due to increase in the nucleation rate of particles during the annealing which is good agreements with the XRD results. EDX elemental analysis showed that the ZF NPs consists of Zn, Fe and O atoms and no other impurities are present. The Fourier transform infrared spectroscopy (FTIR) spectrum having absorption peaks in fingerprint region at 541 cm−1 and 607 cm−1 showing the stretching vibrations of Fe–O and Zn–O bond at tetrahedral and octahedral lattice sites respectively. The optical energy bandgap is decreased from 2.1 eV to 1.9 eV with increase in annealing temperature calculated by diffuse reflectance spectroscopy using Kubelka–Munk function due to increase in the crystallite size. In addition, vibrating sample magnetometer (VSM) showed the superparamagnetic nature of the ZF NPs as M-H curve passing through origin with zero coercivity and remanence.