Effect of sintering conditions on the structural, electrical, and magnetic properties of nanosized Co0.2Ni0.3Zn0.5Fe2O4

The effect of sintering conditions (the temperature and the pressure) on the electrical/dielectric and the magnetic properties of a nanocrystalline Co0.2Ni0.3Zn0.5Fe2O4 was studied. The XRD and EDX results confirmed a single phase nanocrystalline spinel-type ferrite structure of both the as-prepared polyol-made powder and its associated ones sintered between 773 and 1273 K. In addition, analysis of the integrated intensity ratios I220/I222 and I220/I422 indicated changes in the cation occupancy with sintering temperature variation. This result is supported by IR analysis. As expected, the mean particle size inferred from XRD and TEM increased with sintering temperature increase, it ranges from~2 nm for the as-prepared ferrite to~83 nm for the ferrite sintered at 1273 K. The electrical/dielectric properties were investigated over a wide range of frequency and temperature. The sintered ferrites showed a semiconductor behavior with conductivity following the Arrhenius law. At moderately sintering temperatures, the increase of conductivity was attributed to the increase Fe2+ concentration, while, at higher temperatures, the increase is mainly due to the decrease of porosity. The loss factor of our nanoferrites was found to decrease drastically with both the pressure and temperature of sintering showing better values than reported for similar ferrites. Magnetic measurements conducted on a VSM apparatus showed a superparamagnetic behavior at room temperature. In addition, the saturation magnetization was found to increase in a continuous manner with the sintering temperature increase consequence of particle size increase. Finally, the Curie temperature was found to vary slightly between 600 and 631 K, the chemical composition seems to be the main parameter influencing this feature.