Effects of sintering and pressing conditions on the properties of manganese ferrite

In the present work, zinc-manganese ferrite powder with stoichiometric composition Fe2O3-0.5ZnO-0.5Mn3O4 was prepared by mixing the constituent oxides and sintering them. The samples were shaped by two methods: dry powder pressing and slurry pressing with 10% water by weight (after drying), with a pressure of 50 MPa. The samples were sintered in a tube furnace in different oxidizing, neutral, and reducing atmospheres at 1050 °C. Under a neutral argon atmosphere, the porosity was reduced by about 2%, compared to the sintering samples in the oxide state. In order to achieve zero porosity, pressing using a slurry is more effective in small-sized parts. Samples sintered in nitrogen atmosphere, at the same temperature and sintering conditions, had smaller grain sizes compared to those sintered in hydrogen and oxide atmospheres. Based on microstructure comparison, sintering in a hydrogen atmosphere probably led to the formation of the gamma phase in ferrite. The change in magnetic permeability of the samples made by slurry and pressing methods was not significant; with increasing frequency, the permeability increased by about 20% in both cases.