Combustion synthesis of MnFe_2O_4 ferrite powder
Jiang Jiuxing, Li Yao, He Xiaodong, Qu Wei (Center for Composite Materials, Harbin Institute of Technology, Harbin 150001,China)
The spinel MnFe 2O 4 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 composition of the combustion products were also studied by XRD and Mssbauer. The results show that the precent conversion to MnFe 2O 4 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 MnFeO 3 which lead to the higher sintering reactivity of the products. The oxygen pressure and k value have less influnce on the degree of ferritization. Both the degree of the 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 MnFe 2O 4 powders, which have predominantly inverse cation distribution, are obtained by quenching the products at 1200℃ into the air or the water.