Effect of sintering on some properties of NiZn-ferrite

The present investigation reports effect of densification on the magnetic properties (initial permeability and relative loss factor) of Ni–Zn ferrites with a composition (Ni0.68Zn0.25Mn0.02)Fe2.5O4. NiZn-ferrite toroid samples of the above composition, supplied by one industry, were sintered at three temperatures; 1000˚C, 1050˚C and 1100˚C and for three different periods of 15 mins, 1 hr and 4 hrs.The X-ray diffraction pattern confirms the formation of cubic spinel phase. In the above samples, the highest densification achieved was 84.71 % (of theoretical density) at 1100oC 4hrs. The sintering temperature was kept low to minimize the ZnO evaporation loss. Magnetic measurements were performed at 100 KHz (0.01 V) using a LCR meter and showed a maximum inductance of 3.9501 µH. The highest initial permeability was 67.83 and the relative loss factor varied from 0.0143 to 0.00178 i.e. in between the range 10-2 to 10-3. Also, the dependency of permeability and loss were measured in the range of 42 Hz to 1 MHz. A decrease in initial permeability was observed with increasing frequency. Better magnetic properties (at high frequencies) have been noted in the samples with higher densities