Influence Of Process Conditions On The Consistency Of High Permeability Mnzn Ferrite

With the rapid development of communication and science technology in modern society, the information industry will inevitably become the leading industry of human society in the future. MnZn ferrite materials play a very important role because of their excellent performance, and become the basis of electronic information industry. Therefore, MnZn ferrite materials are required for better performance.The production tolerance which determines the electromagnetic performance consistency and yield rate is one of the most important indicators in mass production of MnZn ferrite and an important factor in the competitiveness of makers. It is very difficult to improve the electromagnetic performance consistency of products in the industrial production because of the long process from raw materials to core and the narrow windows of process control during the sintering of high-permeability MnZn ferrite. There are always a range of variations of temperature and atmosphere in a furnace during sintering process, which results in the difference in heat experience among cores and inevitably affects the product consistency. But so far the detailed effect of process conditions on electromagnetic performance consistency is still unclear.In this dissertation, high permeability Mn-Zn ferrites have been prepared by the mixed-oxide route, using high-purity Fe2O3, Mn3O4and ZnO as the raw materials. Then we study deeply on preparation technology and mechanism of high initial permeability MnZn ferrite. The influence of particle size distribution, different additives on the consistency of high permeability of MnZn ferrite were mainly investigate. The main research results are as follows:(1) In this work, high-permeability MnZn ferrite cores were sintered under various sintering temperatures and atmospheres using powders of different particle size distributions to investigate the influence of sintering temperature and atmosphere on the micro structure and magnetic permeability of the sintered cores. It is found that electromagnetic performance of cores made from powders with finer partkle size and narrower size distribution varied less upon the change of sintering temperature and atmosphere. Thus, improving the uniformity of particle size is a good way to increase the permeability consistency of MnZn ferrite in mass production. Tests for this method have been carried out in a factory, primary test results are satisfactory.(2) A large number of studies suggest that with addition of proper quantities of impurities such as Bi2O3, MoO3and SiO2, can improve the grain growth of MnZn to get higher initial permeability MnZn ferrite. In this work, Bi2O3, MoO3and SiO2have been selected. The results show that the consistency of high permeability MnZn ferrite performance reaches best when Bi2O3is50ppm. With MoO3-SiO2-Nb2O5multi-doping, higher initial permeability are obtained. However, this method is not suit for increasing the consistency of initial permeability. Moreover, the consistency of high permeability MnZn ferrite performance is increased with containing proper content of SD2(70ppm), for SiO2can promote grain growth uniformly.(3) High permeability MnZn ferrite performance with containing different content of SiO2has different level of sensitivity to powders of different particle size distribution In order to improve the consistency of initial permeability, we suggest that the content of SiO2additives should increase with the extension of ball mill time.