Microstructures and magnetic properties of sintering Mn–Zn ferrites with additive of different nanosized SiO ₂ particles

Initial permeability μ i and power loss of Mn–Zn ferrites doped with CaO and nano SiO2 with different mean sizes were investigated. With increasing particle size of nano SiO2, the temperature stability of μ i became higher. Meanwhile, the power loss decreased. Microstructure analysis showed that Zn0.4Mn0.6Fe2O4 spinel structure was completely formed in the sintering samples, and SiO2 reacted with CaO to form CaSiO3 at the grain boundary. The effect of different particle sizes of SiO2 on magnetic properties mainly depended on their influence on the grain size and the volume fraction of grain boundary phase. In detail, smaller particle size had higher surface activity under the same sintering condition, which led to excessive grain growth that influenced the grain size and its uniform, and also the volume fraction of grain boundary phase.