Lower dielectric constant Ni-Zn ferrites, obtained by systematic use of microwave sintering

For most applications lower dielectric constants in ferrites are desirable. This study provides a simple blue print to achieve this. Nickel Zinc Ferrites (Ni_1-xZn_xFe₂O₄) with x = 0≤ x ≥ 1 were microwave sintered in a 2.45 GHz microwave fecility for 5, 15, 30, 45 and 60 minutes respectively. All the samples sinter to >95% density with pores distributed evenly throughout the microstructure and pore size showing a general increase in the size and decrease in number density. The microstructural comparison shows that the 30 minutes conventionally sintered sample is indistinguishable from the 5 minutes microwave sintered samples, suggesting that grains grow bigger under the influence of field. Magnetic property data reveal that magnetization values are highest for x = 0.4, thereafter decreases due to spin-spin interaction between Fe³⁺ and Zn²⁺ becomes increasingly "uncoupled". At all frequencies, always lower dielectric constant values were obtained for microwave sintered Ni-Zn ferrites with x = 0.6 and beyond compared to conventional sintering due to possible field-charge interactions.