Synthesis, Microstructure and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite by a Modified Wet Chemical Method

摘要

Nanocrystalline Ni_(1-x)Zn_xFe_2O_4 ferrites with 0 ≤ x ≤ 1 were prepared by spraying-coprecipitation method. The microstructure was investigated by TG-DSC, XRD, SEM, TEM and BET. Magnetic properties were measured with vibrating sample magnetometer at room temperature. The results showed that uniform and fine nanocrystalline Ni_(1-x)Zn_xFe_2O_4 ferrites are obtained. The grain size of sample calcined at 600℃ for 1.5h is about 30nm. There are a few agglomerates with average sizes below 100nm. The specific saturation magnetization, M_s, of the sample increases with increasing Zn~(2+) concent x at room temperature, and the maximum M_s is 66.8 A·m~2·kg~(-1) as the Zn~(2+) content x is around 0.5mol. As calcining temperature increased from 400℃ to 1050℃, the M_s of Ni_(0.5)Zn_(0.5)Fe_2O_4 ferrite increases from 40.2 A·m~2·kg~(-1) to 75.6 A·m~2·kg~(-1). The coercivity maximum is about 5.97 kA·m~(-1) as its critical grain size is about 62.0nm. The relation between coercivity and grain size for nanocrystalline Ni_(0.5)Zn_(0.5)Fe_2O_4 ferrite may be explained based on random anisotropy theory.