Comparison of Magnetic Properties of Low-Temperature-Fired NiCuZn Ferrites Under Low- and High-Bi2O3 Doping Modes

Phase composition, microstructure and magnetic properties of the low-temperature-fired NiCuZn ferrites doped with different concentrations of Bi2O3 were investigated. A proper content of Bi2O3 doping could trigger the formation of a dual microstructure of the ferrites. The before and after ‘critical’ doping content, i.e. low- and high-Bi2O3-doping modes,enabled the ferrites to obtain sufficiently high density and equal permeability. The former sample obtained a uniform, dense and fine-grain-sized microstructure, which was beneficial to improve the high-frequency characteristic and Q-factor characteristic of the low-temperature-fired NiCuZn ferrite; moreover, the saturation flux density was higher. However, the latter sample obtained a uniform, dense and large-grain-sized microstructure with more grain-boundary-dopant, which was beneficial to improve the DC-bias superposition characteristic of the ferrite. These comparative results can essentially guide the engineering applications of the low-temperature-fired NiCuZn ferrites.