A remarkable permeability enhancement of Ni_1-xZn_xFe₂O₄ (x = 0.65 and 0.70), using a multi-compound calcined additive

In this study, entanglement of composition, additive and/or sintering conditions and their effects on magnetic properties of soft ferrites, nickel zinc spinel ferrites (Ni_1-xZn_xFe₂O₄, x = 0.65 and 0.70) which were prepared via conventional solid-state reaction method investigated. Also an equiponderant calcined mixture of Bi₂O₃, CaO, CeO₂, SiO₂, Al₂O₃, Y₂O₃ and nanotitania was mixed thoroughly and used as a multi-compound calcined additive (MCCA). Calcined ferrite powders were crushed, dry and wet milled, dried, mixed with different amounts of MCCA (0.0, 0.5, 1.0, 1.5 and 2.0 wt%), formed in toroidal shapes and finally sintered at different temperatures, from 1150 up to 1360 °C for 3 h. X-ray diffraction assessment confirmed formation of the single phase cubic spinel structures. Initial permeability and Q-factor spectra of the toroids were obtained from 0.1 to 1000 kHz, using an LCR meter. The results show that initial permeability of each sample has a maximum and addition of MCCA to the ferrites leads to a marvelous increase in permeabilities. Additionally, MCCA decreases the optimum sintering temperature too. The optimum amounts of additive were 1.0 and 0.5 wt% for the x = 0.65 (μ' = 492, T_s = 1280 °C) and x = 0.70 (μ' = 478, T_s = 1320 °C), respectively. Permeability spectra illustrate that utility zone of the Ni_0.35Zn_0.65Fe₂O₄ and Ni_0.3Zn_0.7Fe₂O₄ are both less than 100 and 10 kHz, respectively. The results represent that there is a strong entanglement between composition, additive and/or sintering conditions. It can be concluded the MCCA added Ni_0.35Zn_0.65Fe₂O₄, is suitable for application in the switching power supplies.