Research On Temperature Characteristics And DC Superposition Characteristics Of High B_s MnZn Ferrites

With the rapid development of electronic information technology, more and moreelectronic components required that cores must have good performance. For example,the problems of heat dissipation under the environment of high temperature and highfrequency had to be solved when miniaturization of devices was achieved, so the lowpower loss Pcvof cores were required. Besides, under the conditions of high temperatureand high DC superposition, in order to ensure that the saturation magnetic flux densityof cores could not reach maximum quickly and the permeability could not decrease toofast, cores did not only have high B_s, but also high DC superposition characteristics andsuperior frequency dependence. The variation of ions concentration and additive contentinfluencing on temperature characteristics, frequency dependence and DC superpositioncharacteristics of ferrites were studied by means of industralization platform in thispaper.1. High B_sand low loss MnZn power ferritesFor the composition of Mn_0.872-xZn_0.128Fe_2+xO₄, with the increasing of Fe²⁺ionsconcentration x, the secondary maximum peak temperature of permeability μiand thepoint of the minimum Pcvshift to low temperature. Appropriate content of Fe²⁺ions ishelpful to improve DC superposition characteristics. For molecular composition ofMn_0.910-xZn_xFe_2.090O_4.000, as x increases, cut-off frequency frdecreases and then increases.With the increasing superimposed DC, μiincreases firstly and then declines to a certainvalue and tends to be gentle, finally reaches saturation. For molecular composition ofMn_0.782-xZn_0.128Ti_xFe_0.09+2x²⁺Fe_2-2x³⁺O₄, the increasing content of nonmagnetic ion Ti4+does not make B_sdecreased, but B_sincreases, and the permeability is increasingcontinuously, the secondary maximum peak temperature of μiand the point of theminimum Pcvshift to low temperature. For molecular composition ofMn_0.782-xZn_0.128Sn_xFe_0.09+2x³⁺Fe_2-2x³⁺O₄, the substitution of Sn⁴⁺ions can make graingrowth refined and improve frequency dependence and DC superposition characteristicsof ferrites. Appropriate amount of MoO₃is beneficial to liquid phase sintering, whichcan improve sintering density and increase B_s. Excessive MoO₃content can result in abnormal grain growth and increasing porosity. A certain amount of Nb₂O₅additive canpromote grain growth entirely and decrease Pcv. However, excessive Nb₂O₅content canlead to plenty of pores within grains, and the grain growth is abnormal.2. Ultrahigh B_sMnZn ferritesFor molecular composition of Mn_0.506-xZn_0.244Ni_xFe_2.250O₄, when x increases,â…¡peak of permeability shifts to high temperature, DC superposition characteristicsbecomes poor. For molecular composition of Mn_0.653-xZn_0.244Fe_x²⁺Ni_0.103Fe₂O₄, withincrease in x, both μiand B_sdecrease, Pcvincreases continuously. TiO2additive exists atthe grain boundary and hinders grain growth, so the grains growth are refined. Thefrequency dependence and DC superposition characteristics of ferrites are enhanced.