Analysis of power loss in vanadium doped nickel-zinc ferrites

Nickel-zinc ferrite system, Ni_0.65 Zn_0.35 Fe ₂O₄ +×. V₂ O₅, with different vanadium additions from 0.0 wt% to 1.5 wt% in steps of 0.3 wt% has been prepared by conventional ceramic technique. The samples were sintered at 1210 °C for 4 hours in air atmosphere followed by natural cooling. The power loss and microstructures of these materials are examined. Microstructures of the samples reveal that vanadium additions resulted in fine grain structures with no significant variation in grain size with vanadium concentration. The power loss was measured in the frequency range from 100 kHz to 10 MHz under different exciting flux densities from 5 mT to 30 mT, and was analyzed as a function of frequency, composition and maximum exciting flux density. The hysteresis and eddy current losses were separated and analyzed as a function of frequency. The materials have displayed low power losses up to 3 MHz, thus making them suitable for power applications up to this frequency. The hysteresis loss is predominant loss mechanism in the lower frequencies approximately below 200 kHz, and for frequencies above 200 kHz the eddy current loss increases gradually with increasing frequency and becomes predominant in the power loss. The results are explained in terms of the compositional and microstructural modifications brought about by the vanadium additions.