Combustion synthesis of MnFe₂O₄ ferrite powder

The spinel MnFe₂O₄ ferrite powders were prepared by the combustion synthesis method. The dependences of the degree of the ferritization and the combustion wave velocity on the coefficient of the mixture exothermicity k and the oxygen pressure were discussed in detail. The phase compositions of the combustion products were also studied by XRD and Mossbauer. The results show that the percent conversion to MnFe₂O₄ ferrite powders is low (between 35% and 50%) and there are many defects in the structure of the crystal lattice. The combustion products consist of the metastable phases such as MnFeO₃ which lead to the higher sintering reactivity of the products. The oxygen pressure and the k value have less influence on the degree of ferritization. Both the degree of ferritization and the combustion wave velocity increase with the increase of the oxygen pressure, moreover, the extent of the increase is more obvious when the k value is lower. The single spinel phase MnFe₂O₄ powders, which have predominantly inverse cation distribution, are obtained by quenching the products at 1200°C into the air or the water.