Preparation And Properties Study Of Ni-Zn And Mn-Zn Ferrite Laminated Composite Ceramics

The development of technological society cannot be separated from magnetic materials,especially soft magnetic ferrite,which is widely used in communication,aerospace,electronic information,and other industries.MnZn ferrite with high permeability and saturation magnetization and NiZn ferrite with high resistivity and low loss characteristics are the two largest types of soft ferrite used in various working environments,such as transformers,inductors,isolators,phase shifters,and information storage units.With the development of device miniaturization,single-ferrite materials have obvious limitations in application.In order to meet a wider range of applications,this article has designed and implemented two types of ferrites laminated co firing,which can not only meet the requirements of device miniaturization and broadband applications,but also maintain the excellent performance of the two types of ferrites.Firstly,MnZn ferrite powder and NiZn ferrite powder were prepared by ball milling method.The pre-firing temperature was determined to be 930℃,and the secondary ball milling time was 12 h.MnZn ferrite and NiZn ferrite were prepared using spark plasma sintering（SPS）at different sintering temperatures.The best process for preparing MnZn ferrite by spark plasma sintering is sintering temperature of 1000℃and holding time of 3 min.Currently,the saturation magnetization（M_S）is 33.05 emu/g,and the coercivity（H_C）is 11.05Oe.The optimal sintering temperatures for hot pressing sintered NiZn ferrite and MnZn ferrite are 1050℃and 1000℃,respectively,with M_S of 71.13 emu/g and 29.39 emu/g,and H_C of 9.43 Oe and 9.24 Oe,respectively.Secondly,MnZn/NiZn ferrite laminated co fired ceramics were successfully prepared using SPS sintering.The interface between MnZn and NiZn ferrite layers in the co-fired ceramics has no obvious diffusion due to the short sintering time（3 min）and low temperature（～1000℃）.The density and hardness of the co-fired samples increased with the increase of the sintering temperature.The minimum H_C of the co-fired sample is 21.63 Oe,maintaining the low coercivity characteristic of MnZn ferrite.The maximum M_S of the co-fired sample is 51.45 emu/g,and the maximum resistivity is 5.15×10⁶Ω·cm,maintaining the excellent performance of NiZn ferrite.Due to the unique sintering process of SPS technique and the difference in electrical conductivity of the two ferrites,the MnZn ferrite layer is dense while the NiZn ferrite layer is loose in the co-fired ceramics.To adjust the sintering compatibility of NiZn ferrite and MnZn ferrite,the sintering additive Bi₂O₃ was used.After adding additive,the overall microstructure of co-fired layered ferrite ceramics obtained by SPS is uniform and dense.This work provides a simple and feasible method for preparing laminated co-fired ceramics.The process for preparing co-fired ring-column composites using SPS was also explored.Finally,MnZn/NiZn ferrite laminated co-fired ceramics were prepared by hot press sintering.Hot pressing sintering has a long holding time and obvious grain growth,which is conducive to reducing coercivity,but also significantly reducing resistivity.And the interlayer diffusion during hot pressing sintering is more severe than SPS.