Effect of sintering atomosphere on characteristics of grain boundaries in MnZn ferrites

The effect of sintering condition, especially oxygen partial pressure in cooling step, on grain boundary chemistry in MnZn ferrite has been studied. It is found that lower partial pressures of oxygen at higher temperatures induce indistinct grain boundaries, which reduce initial permeability and electrical resistivity. The indistinct grain boundaries are caused by the dissolution of Ca2+ ion into spinel phase. Because of the dissolved Ca+ ion, the secondary peak maximum of initial permeability appears at higher temperature, and seems to be dominated not only by Fe2+ ion but also by other dissolved cations.