Sintering behavior and electromagnetic properties of Fe-deficient NiZn ferrites

Sintering behavior and electromagnetic properties of Ni_0.5Zn_0.5Fe_2−xO_4−3/2x ferrite (x = 0, 0.4, 0.8) by the sol–gel method are investigated. Fe deficiency in the composition enhances sintering and retards grain growth. The near fully dense Fe-deficient samples could be obtained at a sintering temperature as low as 1120 °C and the highest relative density appears in the x = 0.8 sample sintered at 1150 °C. Second phase zincite ZnO resulting from Fe deficiency plays an important role in spinel NiZn ferrites by acting as a grain growth inhibitor and the grain growth of NiZn ferrite is effectively suppressed. When the sintering temperature is above 1200 °C, extensive grain growth occurs due to the probability of serious volatilization of zinc at high temperatures. The ratio of Ni to Zn of NiZn ferrites increases with increasing Fe deficiency due to the separation of zinc from spinel lattice, which results in the decrease in initial permeability and the increase in Curie temperature and resonant frequency.