Co-precipitation Phase Transformation Of Nanosized Mn-zn Ferrite Powders And Their Properties

Magnetic nanomaterial is currently the hot topic of the current research. The soft magnetic ferrite is one of the most important soft magnetic materials with a wide range of applications. In this dissertation, the preparation and properties of soft magnetic MnZn ferrites were discussed.The spinel-type Mn-Zn ferrite nano-powders were sythesized by co-precipitation and refluxing method usingδ-FeOOH as a precursor. The structure and properties of the prepared samples were characterized by XRD, SEM, VSM. The influences of processing parameters such as the pH value of co-precipitation, reaction temperature and reaction time were systematically investigated. The reaction kinetics, thermodynamics, reaction mechanics, magnetic property, thermostability is also studied. The results showed that the optimum refluxing time for complete reaction is 6h. The size of MnZn ferrites nano-powders varied between<10nm and>20nm. It was also found that the mean size of the nano-powders can be controlled by pH value of the co-precipitation solution. As-prepared powders with mean particle size of 20nm and saturation magnetization of 46A·m2/kg were obtained when the pH value is 13.To obtain well-dispersed physical and chemical methods can be used. In this work, physical dispertion was used to decompose the glomeration, and doping agent to obtain stabilization particle. The ultra fine nanoparticles on that aggregation were prepared successfully finally.The effects of Rare-earth (La, Nd, Gd) doping on the structure and magnetic properties of MnZn ferrite nanopowders are discussed in the dissertation. RE ion may either replace Fe3+ and entered into spinel crystal lattice or aggregate on the grain boundary in the form of compound. Due to the difference in available magnetic moment and ion's radius for La3+ Nd3+and Gd3+, the crystal lattice and grain size decreased and the coercive force increased with RE ion doping.