Low-Fire NiO–CuO–ZnO Ferrite with Bi2O3

Abstract

Additions of Bi2O3 were used to enhance densification and to promote grain growth during sintering of NiO–CuO–ZnO ferrite. With a small amount of Bi2O3 (0.5–2.5 wt%) present as a sintering aid in NiO–CuO–ZnO ferrite, the densification rate and final sintered density are greatly increased, but the activation energy of densification is significantly reduced. The grain size of NiO–CuO–ZnO ferrite is significantly increased with the presence of Bi2O3. These results are attributed to the occurrence of a chemical reaction taking place at the interface of Bi2O3/NiO–CuO–ZnO ferrite, resulting in a greater amount of liquid phase and good wetting during sintering. Microstructural analyses show that the above interfacial reaction induces mutual dissolution between Bi2O3 and ferrite, resulting in a reduction of initial magnetic permeability.