Research On NiCuZn Ferrite Magnetic Substrate Material For Wireless Charging And Antenna Structure Design

In recent years,wireless charging technology based on electromagnetic induction principle has been gradually developed.The development trend is higher charging efficiency,higher charging power,and better stability.In order to improve the charging efficiency,one approach is to optimize the design of antenna structure,the other is to add shield in the wireless charging system for enhancing the magnetic induction strength and resistance to metal interference,so as to meet the EMC requirements and improve the wireless charging efficiency.Therefore,the study of antenna structure design,and development of soft magnetic material used to magnetic shielding with high initial permeability,high saturation magnetic induction intensity and low power loss,is of great significance for wireless charging technology.In terms of material research,the preparation of NiCuZn ferrite used to wireless charging by low-temperature sintering is discussed for reducing the energy consumption.The effects of CuO content,single doping,composite doping,prefiring temperature and secondary ball milling process on NiCuZn ferrite and structures properties are systematically studied.The results show that the addition of CuO promotes the sintering densification and grain growth,then reduces the formation temperature of ferrite spinel phase,and maintains good magnetic properties.Li₂CO₃,V₂O₅ and Bi₂O₃ are three kinds of co-solvents which can effectively reduce the sintering temperature of in liquid phase sintering mode.The doping of 0.1wt%Li₂CO₃ can effectively reduce the sintering temperature and obtain the highest concentration of₄)and B_s.But the addition of Bi₂O₃and V₂O₅ sacrifices the magnetic properties.The doping of Bi₂O₃ is more powerful to reduce sintering temperature than that of V₂O₅,but leads to more power loss.Furthermore,compared with doping of only 0.1 wt%Li₂CO₃,the composite doping of 0.1 wt%Li₂CO₃and 0.1 wt%Bi₂O₃ further increases the₄)and B_s,but also increases the P_cv.Besides,optimizing the prefiring temperature and secondary ball grinding time can improve the sintering reactivity and materials performance.In this paper,49.6 mol%Fe₂O₃,30.2 mol%ZnO,10.1 mol%NiO,10.1 mol%CuO were ball-milled for 2.5 hours and pre-sintered at800?,then 0.1 wt%Li₂CO₃ and 0.1 wt%Bi₂O₃ were added,finally,ball-mill for 5 hours and pre-sintering at 940?were employed for the NiCuZn ferrite.The obtained materials used to wireless charging show excellent magnetic properties with 1230 for₄),377 mT for B_s and 400 kW/m³ for P_cv.The influence of antenna structure and migration on coupling performance and efficiency,and the effect of ferritic substrate on the wireless charging system are studied by simulation analysis.On the one hand,the mutual inductance of coupling coils is mainly related to the coupling area,but little affected by coil turns and turns spacing.The coupling coefficient of circular coil is higher than that of rectangular coil.The maximum coupling coefficient of the system is obtained when the outer radius of the receiving coil is slightly larger than that of the transmitting coil.The coil migration seriously reduces the coupling coefficient and transmission efficiency,for example,the transmission efficiency decreases from 98%to about 58%when the migration in x-axis increases from0 mm to 20 mm.On the other hand,the ferrite substrate can resist the interference of metal environment and improve the coupling coefficient.As the magnetic permeability increases to 1000,the coupling coefficient increases to a higher level of 0.83.