Sintering characteristics and magnetic properties of NiCuZn ferrites for MLCI applications

We proposed and experimentally verified that nanocrystalline ferrite particles (NFPs) additive was effective on improving the densification behavior and magnetic properties of the NiCuZn ferrites for multilayer chip inductor (MLCI) applications. The NFPs, which have high surface free energy, spread around the micron-sized ferrite particles (MFPs) and increased contacting area and inter-diffusion of the particles. As a result, densification behaviors of the samples were improved. The sample with 30 wt% NFPs additive exhibited the highest initial permeability when sintered at 900 °C. It was mainly attributed to relatively larger grain size and higher sintering density, and no other sintering aids with different chemical composition were added. Q-factor increased monotonously with the content of NFPs, which was attributed to the decrease of grain size and increase of sintering density. The MLCIs made by the ferrite with 30 wt% NFPs also exhibited better properties than that made by the ferrite with 1.5 wt% Bi2O3 due to less diffusion of Ag electrode to ferrite and higher initial permeability.