Effects of Bi2O3–WO3 additives on sintering behaviors and magnetic properties of NiCuZn ferrites

The effects of mixed Bi2O3–WO3 additives on sintering behaviors and magnetic properties of NiCuZn ferrites were investigated. It was confirmed that appropriate additives of mixed Bi2O3–WO3 could enhance densification of specimens, improve initial permeability and Q-factor of NiCuZn ferrites. This was mainly attributed by that appropriate WO3 additive could improve grain size of the specimen and closed pores are not formed. The maximum initial permeability was achieved with 1.5 wt% Bi2O3 and 0.3 wt% WO3 additives. More WO3 additive may result in the abnormal grain growth and closed pores inside the grain. The multilayer chip inductor made by composition with 1.5 wt% Bi2O3 and 0.3 wt% WO3 additives exhibited relatively lower dc resistivity, higher inductance and Q-factor than the inductor made by NiCuZn ferrite with only Bi2O3 added, this was mainly due to relatively less diffusion of Ag internal electrode and higher initial permeability.