Series Of High Permeability Mnzn Ferrite Materials And Applied Research

With the rapid development of the communications and network technology to the high transmission rate and broadband, Digital Transmission transformers are used widely. Passive components play a decisive role in impedance matching, isolation and signal coupling, and the materials development and device design become a research hotspot. This thesis is selected and researched, in combination with this trend and needs.Firstly, we researched the high permeability and low-loss MnZn ferrite cores materials, which are widely used in ADSL network digital transformers. In the paper, high permeability MnZn ferrites have been prepared by conventional oxide ceramic process. We focus on pre-fire temperature, sintering temperature, sintering atmosphere and a small amount addition of many different oxides on magnetic properties of materials. During the process of research, presintering temperature has a great influence on the micropholopy. Appropriate sintering temperature and sintering atmosphere can significantly improve the magnetic properties of ferrite materials. The introduction of a small amount of CaCO3 can improve the material microstructure, promoting grain growth. Incorporation of Bi2O3 liquid phase sintering can produce material of uniform grain-induced up, the re-introduction of a small amount of MoO3, at the appropriate proportion of under-doped to promote grain growth, sintering density improve, resulting in material improve permeability and reduce the wear and tear. With the introduction of V2O5, increased permeability, after taking the lead in reducing, trace the formation of V2O5 will add the liquid phase sintering, and promote grain growth and lower porosity, add V2O5 over a large number of V5+ ions into the spinel ferrite phase B, and to promote the rapid growth of grain, grain poured into the internal pores, resulting in lower initial permeability, increased wear and tear. Materials finally made the main performance indicators:μi≥10000, tgδ/μi≤1×10-6(10KHz) ,ηB≤0.2×10-3/T (10KHz, 25℃,1.5～3mT).Secondly, we researched the high permeability and high Bs MnZn ferrite cores materials, which are widely used in LAN network digital transformers. In the paper, MnZn ferrites have been prepared by conventional oxide ceramic process. We focus on pre-fire temperature, sintering temperature and additives on the high-permeability magnetic properties of MnZn ferrite materials parameters. During the process of reseach, ZnO content of the main formulations of the material have a great impact on the permeability of materials and Bs. Appropriate pre-sintering temperature is conducive to the ion diffusion time, grain growth, reduce porosity, thereby enhancing the material permeability and saturation magnetic induction. Co2O3 incorporation to increase Bs, reduce Br. MoO3 and TiO2 incorporation of magnetic material can increase the rate of increase in saturation magnetic induction, the effective improvement of the magnetic properties of materials. Materials finally made the main performance indicators:μi≥5000, Bs≥500mT, Br≤130mT, f r≥600KHz.Finally, through the theoretical analysis of pulse transformer in LAN network, using high-permeability and high Bs MnZn ferrite materials to do the main transformer core materials, produced LAN transformer model. Measurement of basic electromagnetic parameters appropriately to meet the design requirements.