Development And Performance Improvement Of MnZn Ferrites With Low Power Loss In A Wide Temperature Range

With the development of EV industry and the demands for electronic components,MnZn ferrites have been developed towards lower power losses and application in wider temperature range.In the sintering process of MnZn ferrites,the element components and the preparation technics play the most important roles.In this work,the influences of sintering temperature,element components and additives were investigated on the physical properties of MnZn ferrites,such as power loss,initial permeability,electrical resistivity,etc.The main works are briefly introduced as follows.?1?MnZn ferrites were prepared by using oxide ceramic tehnology with different sintering temperatures.The crystallinity and the uniformity of grain size were analyzed by employing X-ray diffraction and scanning electron microscopy.The influences of sintering temperature on initial permeability??_i?and magnetic power loss(P_cv)between-30?and 150?were investigated.The results show that,with the sintering temperature of 1300?,the obviously improved uniformity of grain size is obtained,and moreover the temperature stability of initial permeability??_i?and power loss(P_cv)are both improved.?2?MnZn ferrites with different content of Fe₂O₃ were prepared wtih the sintering temperature of 1300?.As the content of Fe₂O₃ increases from 53.6 to54.0mol%,?_i and P_cv changes regularly.As a result,the MnZn ferrite with the best integrated performance is achieved with the content of Fe₂O₃ at 53.70 mol%.Then keeping the Fe₂O₃ content at 53.7 mol%,the magnetic performances are improved slightly with the increase of ZnO content.In the light of the above results,the optimum molar composition is Fe₂O₃:ZnO:MnO=53.70:9.40:36.90?mol%?.For the MnZn ferrite with the best composition,the magnetic properties are obtained as follows:the initial permeability??_i?is 3600 at 25?,saturation magnetic induction?B_s?is 575 mT at 25?and 450 mT at 100?,and the magnetic power loss ranges from290 to 440 kW/m³ when temperature changes between-30 and 150?.?3?The influences of additives such as TiO₂ and NiO were investigated on improving the microstructure and stability of MnZn ferrites.With the doping of TiO₂,the negative magnetocrystalline anisotropy constant K₁ has been compensated,and consequently?_i raises,P_cv declines,and the secondary maximum peak of?_i-T curve moves to lower temperature.Furthermore,the variations of?_i-T and P_cv-T before and after aging test become smaller compared with the sample without TiO₂.Overall,the reliabilities of MnZn ferrites have been improved enormously with the doping of TiO₂.When NiO is added to the system from 0 to 2500 ppm,the grain size becomes smaller but more uniform first,and then become worse again.With the doping of NiO,the stability of magnetic properties in a wide temperature range has been disappeared.The changes of?_i and P_cv are enormously dependent on the temperature.Furthermore,the sample's flatness of P_cv-T between 80?and 150?has been enhanced.