The influence of grain boundary internal stress on permeability: temperature curve for Mn–Zn ferrites

Abstract The oxygen partial pressure ( P O 2 ) utilized in homogenization or cooling stage of sintering process has been observed to significantly influence the initial permeability-temperature ( μ i – T ) characteristics of the materials. Higher oxygen partial pressure ( P O 2 ) during homogenization period lowers the μ i -value without shifting the secondary maximum peak ( T smp ). However, higher P O 2 (0.1%) during cooling period shifts the T smp toward lower-temperature regime. This phenomenon is accounted for by the induction of compressive stress onto the ferrite grains, which in turn, is due to preferential oxidation along grain boundaries.