| With the rapid development of information technology and microwave communication technology,functional materials and information devices are also constantly innovating,the social industrial development has put forward higher requirements for the preparation methods,characterization technologies,and performance tests of functional composite media.Functional composite media is a multi-phase composite media composed of a variety of materials with excellent characteristics.Among them,ferromagnetic/ferroelectric composite media have both the dielectric response performance of ferroelectric materials and the magnetic tunability of ferromagnetic materials.Taking advantage of weaknesses in performance and producing synergistic effects,it has become a research focus of functional composite media.Researchers generally study the performance of specific ferromagnetic/ferroelectric composite media at high and low frequencies,but there is not much research on the effect of different ferromagnetic/ferroelectric material composite ratios on the performance of composite media.In view of this situation,in this thesis,by setting different mass fractions of yttrium iron garnet(Y3Fe5O12,YIG)and barium strontium titanate(Ba0.5Sr0.5TiO3,BST),the composite ratio of the two was changed to prepare(1-x)YIG—xBST(x=0.1,0.2,0.3,0.4,0.5)composite media and systematic research.In this study,a solid-phase reaction method was used to prepare a composite medium at 1300?.In order to prove that each phase in the composite medium exists independently,phase analysis and morphology analysis were performed on it.The XRD diffraction pattern of composite medium shows the main crystal phases of the sintered samples are the BST phase and the YIG phase,and the two phases exist independently.The scanning electron microscope test confirmed that the sintered ceramic grains have grown completely and distributed uniformly.In addition,the energy spectrum analysis of the composite medium has further proved that the YIG and BST phases are independent and distributed.In order to reveal the relationship between temperature,frequency,and the composite ratio of different magnetoelectric materials and the dielectric properties of the composite media,the sintered samples were tested for dielectric properties.The test results show that the dielectric constant of the(1-x)YIG-xBST(x=0.1,0.2,0.3,0.4,0.5)composite media increases significantly with the increase of BST mass fraction at room temperature and frequency of 1 MHz,the dielectric loss decreases sharply and then remains stable;at room temperature,as the frequency increases from 102 Hz to 106 Hz,the dielectric constant and dielectric loss of the composite media gradually decrease;as the temperature increases from room temperature to 400?,the dielectric constant and dielectric loss of the composite medium of each component at each frequency gradually increase.Afterwards,samples with good dielectric properties are selected and cut into pieces for magnetic performance testing.The composite medium exhibits the typical hysteresis loop shape of a soft magnet.With the increase of the BST mass fraction,the saturation magnetization(Ms)of the composite medium gradually decreases,the magnetic permeability decreases significantly,and it stabilizes after the magnetic loss decreases sharply.Based on the results of the composite media performance obtained above,the performance of the composite media unit structure and metamaterial structure in the waveguide was further explored.The test results show that the(1-x)YIG-xBST(x=0.2,0.3,0.4,0.5)composite media metamaterial structure shows obvious magnetic tunability in the waveguide,and the tunability performance caused by different composite ratios is different.This study confirms the adjustable electric and magnetic fields of ferromagnetic/ferroelectric materials,and designs a composite media metamaterial structure that can be used for tunable microwave devices,and it will have great application prospects in the field of tunable microwave devices. |
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