Effects of Al2O3 addition on the DC--bias-superposition characteristic of the low-temperature-fired NiCuZn ferrites

Abstract

Low-temperature-fired NiCuZn ferrites with Al2O3 (0–2 wt%) addition were prepared via the conventional solid-state reaction. The effects of different Al2O3 doping contents on phase composition, microstructure and magnetic properties, especially DC-bias-superposition characteristic, were investigated. Results indicated that the addition of an appropriate amount of Al2O3 content to NiCuZn ferrites could increase coercivity and the thickness of the nonmagnetic grain boundaries, thereby increasing the demagnetising field and subsequently reducing the decrease rate of the magnetic permeability under superposition magnetic fields. Simultaneously, permeability and saturation flux density monotonously decreased with the increase in Al2O3 doping content. With the addition of 1.5 wt% Al2O3, the sample obtained relatively high permeability (∼70.7) and perfect DC-bias-superposition characteristic (H70%–840 A/m). This ferrite material has favourable application prospects for recognising chip inductors that can carry large currents.