Investigation On The Composite Doping And Ion Regulation Of Low Temperature Sintered NiCuZn Ferrites

In recent years,with the rise of emerging new technologies such as 5G mobile communication,microwave and millimeter-wave communication,modern detection communication,artificial intelligence and mobile terminals,the market has also put forward more new requirements for electronic components,especially the miniaturization,high-frequency,integration,high performance and multi-function.Therefore,electronic materials are the foundation and key to achieve all this.Electronic components based on ferrite have the characteristics of high efficiency,high performance,small size and low cost,and they play an important role in the preparation of some electronic components today.Among them,Ni Cu Zn ferrites have the advantages of high permeability,high resistivity and high saturation magnetization,and the narrow ferromagnetic resonance line width,etc.,and it is an extremely important ferrite material.Furthermore,the advent of the portable electronic age has driven the development of ferrite devices towards smaller,lighter,more integrated and higher performance.Low temperature co-fired ceramic?LTCC?technology can well realize the miniaturization and integration of devices.However,low-temperature sintered ferrites in accordance with the LTCC technology required the sintering temperature of Ni Cu Zn ferrite to be lower than 960 ^oC?co-fired with silver electrode?.Then the problems such as insufficient grain growth,poor densification,and mul-pores,etc will be produced,which will deteriorate the device performance.Meanwhile,on the basis of realizing the diversification of materials,exploring the gyromagnetic properties of low-temperature sintered Ni Cu Zn in the microwave range is a hot issue to be solved,and it is of great significance to expand the wider application of Ni Cu Zn ferrite.This dissertation focused on the wide-band low temperature sintered Ni Cu Zn ferrites,including improving the soft magnetic properties in the radio frequency domain and exploring the gyromagnetic magnetic properties in the microwave band.The microstructure,soft magnetic and gyromagnetic magnetic properties of low-temperature sintered Ni Cu Zn ferrites were controlled and optimized by using metal cation substitution,low melting point oxide composite doping,and different sintering processes.In particular,with the new requirements of 5G technology for high frequency electronic components,the gyromagnetic properties of Ni Cu Zn ferrites in the microwave band were further explored,and the key factors and internal mechanisms affecting the variation of its ferromagnetic resonance linewidth were analyzed.Then,a X band phase shifter was designed,simulated and manufactured to verify the materials.Firstly,the influences of Bi³⁺ion-substituted Ni Cu Zn ferrite on its microstructure,dielectric properties,and magnetic properties were systematically investigated.The activation energy of Ni Cu Zn ferrite was reduced by adding Bi₂O₃ in the pre-burning stage,and the sintering temperature was successfully reduced.The results showed that:when the sintering temperature was 900 ^oC and x=0.025,the uniform and dense Ni Cu Zn ferrites with the permeability??=29.1?@1 MHz?,the permittivity??=17.8,the cut-off frequency f_r=200 MHz,impedance matching coefficient Z=1.28,magnetic loss tan?_?=8.53×10^-3 and dielectric loss tan?_?=1.22×10^-4 were synthesized at low temperatures.Then,Bi³⁺ion-substituted Ni Cu Zn ferrites with the gyromagnetic properties were further investigated.These studies found that:when sintered at 925 ^oC,and the substitution amount of Bi₂O₃ was 0.05,4?M_s increased from 1408 Gauss to3760 Gauss,and?H decreased from 1050 Oe to 248 Oe,indicating that the ferrite can be well applied in microwave phase shifter.Secondly,to further optimize the high frequency magnetic properties of Ni Cu Zn ferrite at low temperatures by ion substitution method,Mn³⁺ion-substitution Ni Cu Zn ferrite is proposed to control the microstructure and properties of the samples sintered at low temperatures.The results showed that Mn³⁺ion substituted into Ni Cu Zn Fe³⁺ion reduced the total magnetic moment of the samples and thus reduced the saturation magnetization.At 880 ^oC sintering,when the amount of Mn₂O₃ additives were 0.25,the initial permeability was 219,and the cut-off frequency was up to 58 MHz.Moreover,when sintering temperature was 900 ^oC,it has excellent gyromagnetic magnetic:H_c was141 Oe,remanence ratio was 0.792,4?M_s was 3872 Gauss,?35?H was 161 Oe.Then,the effects of the composite addition of Mn O₂-Bi₂O₃ on the microstructure and magnetic properties of low sintering temperature Ni Cu Zn ferrite were investigated.Under the composite additives doping,the compactness and uniformity of Ni Cu Zn ferrite grains sintered at a low temperature were achieved.The results showed that:?1?when the sintering temperature was 925 ^oC and 0.5 wt.%Mn O₂-1.5 wt.%Bi₂O₃composite doping,Ni Cu Zn ferrites had the optimal soft magnetic properties:the initial permeability?=291,Q=75,B_s=290 m T and f_r=18 MHz.?2?when the sintering temperature was 950 ^oC and 0.5 wt.%Mn O₂-1.5 wt.%Bi₂O₃ composite doping,the sample had the optimal gyromagnetic properties:4?M_s=3812.23 Gauss,H_c=84.93 Oe and?H=144.6 Oe.In addition,an optimized transient sintering method was designed to explore the ferromagnetic resonance linewidth of Ni Cu Zn ferrite with small grains.Finally,the Ni Cu Zn ferrites with the average grain size was only 0.64?m,4?M_s=3904Gauss and?H=170 Oe were prepared.Moreover,for Bi₂O₃-Nb₂O₅ composite doping Ni Cu Zn ferrite,quantitave Bi₂O₃ is selected to promote the grain growth of low-temoerature sintered Ni Cu Zn ferrite,and the microstructure and magnetic properties of the Ni Cu Zn ferrites with larger grains were optimized by adjusting the additive amount of Nb₂O₅.The results showed that when the sintering temperature was 900 ^oC and 1.0 wt.%Bi₂O₃-0.2 wt.%Nb₂O₅composite doping,the saturation magnetization of the samples increased increased from42.68 emu/g to 54.39 emu/g,and the initial permeability was up to 410.Additionaly,when doped with 1.0 wt.%Bi₂O₃-0.2 wt.%Nb₂O₅,the samples also have excellent gyromagnetic properties:4?M_s=3506 Gauss,?35?H=162.63 Oe.Further,the sintering temperature and time of the samples were changed on the basis of optimized composite doping,and the relationship between the changes of microstructure caused by grain growth and the ferromagnetic resonance line width were studied.Finally,A chip inductor was designed and simulated by selecting 0.5 wt.%Mn O₂-1.5 wt.%Bi₂O₃ composite doped Ni Cu Zn ferrite sintered at 925 ^oC as the matrix material.At the same time,0.5 wt.%Mn O₂-1.0 wt.%Bi₂O₃ composite doped Ni Cu Zn ferrite block sintered at 950 ^oC was selected to be cut and polished as the substrate for X-band phase shifter.A HFSS simulated microstrip line phase shifter circuit was lithography to the substrate,and the phase shifter test was completed under the built test platform.The results showed that at the central frequency 9.55 GHz,the phase shift was252°,the S₂₁ was-2.49 d B,S₁₁ was-19.31 d B,which indicating that this low temperature sintering Ni Cu Zn ferrites can be well applied to microwave devices.