Morphology and dielectric properties of single sample Ni_0.5Zn_0.5Fe₂O₄ nanoparticles prepared via mechanical alloying

Nickel–zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials. Nickel–zinc ferrite nanoparticles with composition Ni_0.5Zn_0.5Fe₂O₄ were prepared using mechanical alloying to analyze the effect of sintering temperature on microstructure evolution of a single sample with dielectric properties. The single sample with nanosized pellet was sintered from 600 ℃ to 1200 ℃ and analyzed by X-ray diffraction (XRD) to investigate the phases of the powders and by field emission scanning electron microscopy (FESEM) for the morphology and microstructure analyses. Dielectric properties such as dielectric constant ( ${\epsilon }^{\prime }$) and dielectric loss ( ${\epsilon }^{″}$) were studied as functions of frequency and temperature for Ni_0.5Zn_0.5Fe₂O₄. The dielectric properties of the sample were measured using HP 4192A LF impedance analyzer in the low frequency range from 40 Hz to 1 MHz and at temperature ranging from 30 ℃ to 250 ℃. The results showed that single phase Ni_0.5Zn_0.5Fe₂O₄ cannot be formed by milling alone and therefore requires sintering. The crystallization of the ferrite sample increased with increasing sintering temperature, while the porosity decreased and the density and average grain size increased. Evolution of the microstructure resulted in three activation energies of grain growth, where above 850 ℃ there was a rapid grain growth in the microstructure. Dielectric constant and loss factor decreased with the increase in frequency. The optimum sintering temperature of Ni_0.5Zn_0.5Fe₂O₄ was found to be 900 ℃ which had high dielectric constant and low dielectric loss.