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Study on the Properties of Ni-Zn Ferrites Prepared by Using Nano-Size ZnO

The present work reported and discussed the results of investigation of employing nano-ZnO and general ZnO (AR grade) to prepare Ni0.5Zn0.5Fe2O4 ferrites. The samples were prepared by using conventional ceramic processing route and sintered between 1150-1250 o C. The comparison of sintered samples made by employing nano-ZnO and made by employing general ZnO powder shows that the use of nano-ZnO could increase the chemical activity of starting materials, improve the densification and homogeneity of sintered bodies, enhance the electrical and magnetic properties of Ni-Zn ferrites. Sample Preparation. The ferrite samples used in this study were based on a typically commercial formula: Ni0.5Zn0.5Fe2O4. All starting materials were analytic grade oxides, the average particle size of nano-ZnO is about 60 nm. They were mixed in deionised water with agate balls for 20 hours by ball milling. After drying, granules were obtained by passing the dried powders through a screen having an aperture mesh of nominally 0.3mm. The small disc shape samples (12mm diameter, 3mm height.) and the toroid samples (25mm outside diameter, 18mm inside diameter, and 3mm height) were pressed by a uniaxial press at 80MPa. The samples were sintered at temperatures over the range 1150-1250 o C for 2 hours in air, with both heating and cooling rates at 3 o C/min. The samples prepared by general chemicals were designated as C samples, and the samples prepared by nano-ZnO were designated as N samples. Characterization. The sintered densities of the samples were determined according to the mass and volume of sample. Before electrical measurements, sliver electrodes were applied to both sides of the disc samples. The resistances of disc samples were determined by using a LCR meter (Victor VC9018). The resistivities were computed out according to the measured resistances and the