Effects of calcining and sintering parameters on the magnetic properties of high-permeability MnZn ferrites

For asymmetric digital subscriber line (ADSL) technology applications, new MnZn ferrites are required with not only high initial permeability, but also with low hysteresis material constant η_B. The effects of calcining and sintering temperatures and oxygen equilibrium partial pressure on the magnetic properties of MnZn ferrites are studied in this work. It was found that raising the calcining temperature required a rise in the sintering temperature to simultaneously achieve maximum permeability and the lowest η_B value. Both grain size and porosity had an effect on the initial permeability of the samples. Porosity had an even larger effect on the η_B value than the initial permeability. Oxygen equilibrium partial pressure also had an important effect on the initial permeability and η_B value. In our testing range, both the initial permeability and the η_B value decreased with increasing value of A (oxygen parameter). In order to optimize synthesis conditions for the high initial permeability and low η_B value, it was best to calcine the sample at 950°C and sinter it at 1370°C, with A=7.55.