Low-temperature-fired NiCuZn ferrites with BBSZ glass

Addition of BBSZ (27% Bi2O3, 35% H3BO3, 6% SiO2, and 32% ZnO in mol%) glass has been used to enhance densification and improve the magnetic properties of low-temperature-fired NiCuZn ferrites. It was found that the BBSZ glass did not form a visible second phase in our testing range. However, the densification and microstructure of the ferrites were initially very sensitive to the BBSZ glass content. Even a slight increase in BBSZ glass content from 0.25 to 0.5 wt% was sufficient to change the ferrite samples from not being well sintered with a uniform microstructure and very small grain size to a typical bimodal, inhomogeneous microstructure. It proved to be better to add more BBSZ glass than the critical content to obtain the appropriate microstructure and magnetic properties. In this study, a ferrite sample with 0.75 wt% BBSZ glass gave the best performance in terms of densification, microstructure, permeability, and Q-factor characteristics.

Research highlights
► BBSZ glass was added to NiCuZn ferrites as a sintering aid first time.
► BBSZ glass obviously enhanced the densification and influenced the microstructure.
► It was better to add more BBSZ glass than the critical content to obtain the appropriate properties.
► 0.75 wt% proved to be the optimal content for the NiCuZn ferrites with BBSZ glass.