Effects of tungsten trioxide addition and top-temperature sintering period on properties of high-permeability NiCuZn ferrite

We examined the effects of added WO3 and top-temperature sintering period on initial permeability and other material characteristics in order to develop NiCuZn ferrites with a high permeability. It was found that to obtain a single-phase spinel ferrite, the content of WO3 addition should be less than 0.28 wt%. With proper WO3 addition, average grain size and initial permeability of the ferrite increased obviously. However, overfull WO3 addition lead to increase of porosity and impeded grain growth. As a result, the initial permeability increased, peaked, and then gradually declined under the influence of WO3 addition. The maximum initial permeability was observed at a WO3 content of 0.16 wt% with 3-h top-temperature sintering. Furthermore, by prolonging the top-temperature sintering period to curb porosity, it was possible to obtain a higher permeability of the NiCuZn ferrite.