Precise control of the sinter process (with temperature and oxygen partial pressure as crucial parameters) is a key element in the preparation of Mn-Zn ferrites for low-loss power ferrites. We report about sintering experiments of ferrites at 1300°C with a cooling regime according to relation log pO2 = a-b/T with the parameter a ranging from 8... 15 and b ≈ 21.000. Although the microstructures of all samples are similar, the ferrites cooled in relatively low oxygen partial pressure (i.e. close to the stoichiometric spinel phase) have low losses, whereas samples cooled at more oxidizing conditions (closer to the upper ferrite phase boundary) show high losses. Moreover, we demonstrate the effects of powder morphology and oxygen partial pressure control during heating. Increased density and reduced losses are a result of lower oxygen pressure during heating.
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