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UltrahighQ Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)microwave dielectric ceramics for temperature-stable millimeter-wave dielectric resonator antennas

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Journal of Advanced ceramics 2024年第2期13卷 155-165页

作者： Guoqiang He Yu Jiang Kaixin Song Yanjun Liu Yuan Nie Wenjie Zhang Ziqi Zhao Yinghan He Xinyue Ma Xiuli Chen Xu Li Huanfu Zhou Collaborative Innovation Centre for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi Key Laboratory of Nonferrous Materials and New Processing TechnologyMinistry of EducationSchool of Materials Science and EngineeringGuilin University of TechnologyGuilin 541004China College of Electronic Information Hangzhou Dianzi UniversityHangzhou 310018China

microwave dielectric ceramics should be improved to advance mobile communication technologies further.In this study,we prepared Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics with nonstoichiometric Sr^(2+)ratios based on our previously reported SrY_(2)O_(4) microwave dielectric ceramic,which has a low dielectric constant and an ultrahigh quality factor(Q value).The ceramic exhibited a 33.6% higher Q-by-frequency(Q×f)value(Q≈12,500)at x=0.02 than SrY_(2)O_(4).All Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics exhibited pure phase structures,although variations in crystal-plane spacings were observed.The ceramics are mainly composed of Sr-O,Y1-O,and Y_(2)-O octahedra,with the temperature coefficient of the resonant frequency(τ_(f))of the ceramic increasing with Y_(2)-O octahedral distortion.The ceramic comprises uniform grains with a homogeneous elemental distribution,clear grain boundaries,and no obvious cavities at x=0.02.The Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics exhibited good microwave dielectric properties,with optimal performance observed at x=0.02(dielectric constant(εr)=15.41,Q×f=112,375 GHz,and τ_(f)=-17.44 ppm/℃).The τ_(f) value was reduced to meet the temperaturestability requirements of 5G/6G communication systems by adding CaTiO_(3),with Sr_(1.02)Y_(2)O_(4.02)+2wt% CaTiO_(3) exhibiting ε_(r)=16.14,Q×f=51,004 GHz,andτf=0 ppm/℃.A dielectric resonator antenna prepared using Sr_(1.02)Y_(2)O_(4.02)+2wt%CaTiO_(3) exhibited a central frequency of 26.6 GHz,with a corresponding gain and efficiency of 3.66 dBi and 83.14%,respectively.Consequently,Sr_(1.02)Y_(2)O_(4).02-based dielectric resonator antennas are suitable for use in 5G millimeter-wave band(24.5-27.5 GHz)applications.

关键词： millimeter wave microwave dielectric ceramics dielectric resonator antenna nonstoichiometric ratio

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Structure,defects,and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba_(4)Nd_(9.33)Ti_(18)O_(54)ceramics

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Journal of Advanced ceramics 2022年第4期11卷 629-640页

作者： Weijia GUO Zhiyu MA Yu LUO Yugu CHEN Zhenxing YUE Longtu LI State Key Laboratory of New ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Low-loss tungsten–bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation(5G)communication technology.In this work,a novel Al/Nd co-doping method of Ba_(4)Nd_(9.33)Ti_(18)O_(54)(BNT)ceramics with a chemical formula of Ba_(4)Nd_(9.33+z/3)Ti_(18−z)Al_(z)O_(54)(BNT–AN,0≤z≤2)was proposed to improve the dielectric properties through structural and defect modulation.Together with Al-doped ceramics(Ba_(4)Nd_(9.33)Ti_(18−z)Al_(4z/3)O_(54),BNT–A,0≤z≤2)for comparison,the ceramics were prepared by a solid state method.It is found that Al/Nd co-doping method has a significant effect on improving the dielectric properties compared with Al doping.As the doping amount z increased,the relative dielectric constant(εr)and the temperature coefficient of resonant frequency(τf)of the ceramics decreased,and the Q×f values of the ceramics obviously increased when z≤1.5.Excellent microwave dielectric properties ofεr=72.2,Q×f=16,480 GHz,andτf=+14.3 ppm/℃were achieved in BNT–AN ceramics with z=1.25.Raman spectroscopy and thermally stimulated depolarization current(TSDC)technique were firstly combined to analyze the structures and defects in microwave dielectric ceramics.It is shown that the improvement on Q×f values was originated from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies(VO××),demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.

关键词： microwave dielectric ceramics Ba4Nd9.33Ti18O54(BNT) Al and Al/Nd doping structural and defect modulation

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Crystal structure and enhanced microwave dielectric properties of the Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9) ceramics at microwave frequency

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Journal of Advanced ceramics 2022年第3期11卷 392-402页

作者： Chao FENG Xu ZHOU Bingjing TAO Haitao WU Shifeng HUANG Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials University of JinanJinan250022China School of Environmental and Material Engineering Yantai UniversityYantai264005China

Dense microwave dielectric ceramics of Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) (x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al1/2Ta1/2)^(4+) on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr_(2)Zr_(3)(MoO_(4))_(9) structures, which belonged to the space group R3¯c. The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips—Van Vechten—Levine (P—V—L) theory. Excellent dielectric properties of Ce_(2)[Zr_(0.94)(Al_(1/2)Ta_(1/2))_(0.06)]_(3)(MoO_(4))_(9) with a relative permittivity (ε_(r)) of 10.46, quality factor (Q × f) of 83,796 GHz, and temperature coefficient of resonant frequency (τ_(f)) of −11.50 ppm/℃ were achieved at 850 ℃.

关键词： microwave dielectric ceramics Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) Phillips-Van Vechten-Levine(P-V-L)theory low sintering temperature

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Crystal structures and microwave dielectric properties of Sr_(2)MgWO_(6) ceramics at different sintering temperatures

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Journal of Materiomics 2022年第1期8卷 79-87页

作者： Jiqing Lv Zhikai Cao Yuying Wang Feng Shi Jing Wang School of Material Science&Engineering Shandong University of Science and TechnologyQingdao266590China School of Materials Science and Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan250353China

Sr_(2)MgWO_(6)(SMW)is a typical perovskite oxide compound,but there has been little research on the effects of processing on its dielectric properties.In this work,SMW ceramics were prepared by solid-state synthesis with sintering at 1450℃,1475℃,1500℃and 1525℃,respectively.XRD results confirmed that the samples possessed double perovskite structure(Fm-3m).The Raman and FTIR spectra were used to study the lattice vibrational modes.The FPSQ model was used to obtain the fitting curves of the FTIR spectra and derive the intrinsic properties of the material that were found to be in agreement with the measured data.The structure-property relationships were successfully established based on the Raman mode results.The optimal sintering temperature of SMW ceramics was identified as 1475℃due to the excellent performances characteristics(ε_(r)=16.97,Q×f=23,872 GHz,τ_(f)=-35.38 ppm/℃)obtained at this temperature.This study explored the relationships among the crystal structures,lattice vibrational characteristics and dielectric properties of SMW ceramics,so as to further understand their dielectric response mechanism and lay a solid theoretical foundation for the development of microwave ceramics.

关键词： microwave dielectric ceramics Crystal structures Intrinsic properties Lattice vibrational characteristics Structure-property relationships

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Machine learning approaches for permittivity prediction and rational design of microwave dielectric ceramics

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Journal of Materiomics 2021年第6期7卷 1284-1293页

作者： Jincheng Qin Zhifu Liu Mingsheng Ma Yongxiang Li CAS Key Laboratory of Inorganic Functional Materials and Devices Shanghai Institute of CeramicsChinese Academy of SciencesShanghai201899China Center of Materials Sciences and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing100049China

Low permittivity microwave dielectric ceramics(MWDCs)are attracting great interest because of their promising applications in the new era of 5G and IoT.Although theoretical rules and computational methods are of practical use for permittivity prediction,unsatisfactory predictability and universality impede rational design of new high-performance materials.In this work,based on a dataset of 254 single-phase microwave dielectric ceramics(MWDCs),machine learning(ML)methods established a high accuracy model for permittivity prediction and gave insights of quantitative chemistry/structureproperty relationships.We employed five commonly-used algorithms,and introduced 32 intrinsic chemical,structural and thermodynamic features which have correlations with permittivity for modeling.Machine learning results help identify the permittivity decisive factors,including polarizability per unit volume,average bond length,and average cell volume per atom.The feature-property relationships were discussed.The optimal model constructed by support vector regression with radial basis function kernel was validated its superior predictability and generalization by verification dataset.Low permittivity material systems were screened from a dataset of~3300 materials without reported microwave permittivity by high-throughput prediction using optimal model.Several predicted low permittivity ceramics were synthesized,and the experimental results agree well with ML prediction,which confirmed the reliability of the prediction model.

关键词： microwave dielectric ceramics Low permittivity ceramics Permittivity prediction Machine learning Quantitative structure-property relationship

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Room-temperature-densified H_(3)BO_(3) microwave dielectric ceramics with ultra-low permittivity and ultra-high Qf value

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Journal of Materiomics 2020年第2期6卷 233-239页

作者： Wen Bin Hong Lei Li Han Yan Shu Ya Wu Hang Sheng Yang Xiang Ming Chen Laboratory of dielectric Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou310027China

With the rapid development of mobile communication technology towards 5G and 6G,the microwave dielectric materials with ultra-low permittivity and ultra-high Qf value are urgently demanded.Here,the excellent microwave dielectric properties are reported in H3BO3 ceramics with the molecular crystal structure,whose permittivity(2.84)and density(1.46 g/cm^(3))are record-low among the low-loss ceramics.The ultra-high Qf value of 146,000 GHz(or the ultra-low dielectric loss of 1.03×10^(-4) at 15 GHz)is also distinguished.Besides,the H_(3)BO_(3) ceramics can be densified at room temperature by a simple cold sintering process in a short time of 10 min,and this brings many advantages for the integration with microwave circuits.The large molecule volume originating from the molecular crystal structure and the low dielectric polarizabilities of H^(+) and B^(3+) are responsible for the ultra-low permittivity of H_(3)BO_(3) ceramics,and more microwave dielectric materials with ultra-low permittivity and ultra-high Qf value are expected to be explored in the molecular crystals.

关键词： Boric acid microwave dielectric ceramics Room-temperature cold sintering Ultra-low permittivity

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Improved microwave dielectric properties of MgAl_(2)O_(4)spinel ceramics through(Li_(1/3)Ti_(2/3))^(3+)doping

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Chinese Physics B 2023年第5期32卷 668-673页

作者：李潇杨习志赖元明张芹李宝阳戚聪殷俊王凡硕巫崇胜苏桦 School of Mechanical and Electrical Engineering Chengdu University of TechnologyChengdu 610059China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054China

A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.

关键词： microwave dielectric ceramics MgAl_(2)O_(4)ceramic co-substitution MgTi_(2)O_(5) solid solubility limit

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Effect of La_2O_3-Dopant on Microstructure and microwave dielectric Properties of CaO-MgO-Nb_2O_5-TiO_2 System ceramics

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Journal of Rare Earths 2005年第1期23卷 32-35页

作者：王浩陈文刘涛 Institute of Materials Science and Engineering Wuhan University of Technology Wuhan 430070 China

La_2O_3-doped CaO-MgO-Nb_2O_5-TiO_2 system ceramics were prepared by solid-state ceramic technique. The microstructure and microwave dielectric properties of CaO-MgO-Nb_2O_5-TiO_2-La_2O_3 ceramics can be adjusted by varying the amount of La^(3+) ions. The results show that the replacement of Ca^(2+) by La^(3+) at A-site of the ceramics can increase the quality factor Q·f value as well as the temperature coefficient of resonant frequency τ_f and decrease the dielectric constant ε_r. With increase of La^(3+) contents, the dielectric constant decreases from 57 to 35 and Q·f value increases from 33400 GHz to 35000 GHz (at 7.6 GHz). Meanwhile, the temperature coefficient of resonant frequency is improved towards near zero. The dielectric properties of these compounds are related to octahedra tilting due to deficient vacancies at A-site.

关键词： inorganic nonmetallic materials perovskite microwave dielectric ceramics dielectric properties rare earths

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microwave dielectric properties of Ba_(6-3x)La_(8+2x)(Ti_(1-z)Zr_z)_(18)O_(54)(x=2/3) ceramics

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Journal of Rare Earths 2010年第3期28卷 411-415页

作者：高旭芳丘泰 College of Materials Science and Engineering Nanjing University of Technology

Zr substitution for Ti was investigated to modify the dielectric properties of Ba6-3xLa8+2xTi18O54(x=2/3) ceramics.A single-phase solid solution with tungstenbronze-like structure was formed in the range of 0ceramics.As Zr content exceeded this range,a secondary phase of Ba2ZrO4 was detected.This is correlated with the decrease of tolerance factor.As Zr content increased,there was an expansion of the b-axis and c-axis,and increase in the cell volume.Incorporation ...

关键词： dielectric properties microwave dielectric ceramics substitution tungstenbronze-like structure rare earths

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Synthesis,crystal structure and microwave dielectric properties of self-temperature stable Ba_(1-x)Sr_(x)CuSi_(2)O_(6) ceramics for millimeter-wave communication

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Journal of Materiomics 2019年第4期5卷 606-617页

作者： Xiao-Qiang Song Meng-Qi Xie Kang Du Wen-Zhong Lu Wen Lei School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan430074China Key Lab of Functional Materials for Electronic Information(B) Ministry of EducationWuhan430074China

Ba_(1-x)Sr_(x)CuSi_(2)O_(6) compounds with a tetrahedral structure(I41/acd)were prepared through the solid-state reaction method.The phase building process,structural evolution and microwave dielectric properties of Ba_(1-x)Sr_(x)CuSi_(2)O_(6) were investigated.Single BaCuSi_(2)O_(6) phase can be obtained when calcined at 1050℃ for 3 h or 950℃ for 10 h.The substitution of Ba^(2+) by Sr^(2+) can effectively promote the sintering process and the maximum solubility of Ba_(1-x)Sr_(x)CuSi_(2)O_(6) was located between 0.25 and 0.30.Rietveld refinement,Raman-spectra and P-V-L complex chemical bond theory were used to explain the correlations between the crystal structures and microwave dielectric properties.The dielectric constant was dominated by the susceptibility(Σχ^(μ))and ionic polarizability.The quality factor(Q×f)was determined by the bond strength,packing fraction and lattice energy,especially the Si-O bond.The susceptibility of Cu-O bond and Si-O bond played an important role in controlling the temperature coefficient of the resonant frequency(τf).A near zero τf value was obtained at x=0-0.10 and the optimum microwave dielectric properties for Ba_(1-x)Sr_(x)CuSi_(2)O_(6) were achieved at x=0.20 when sintered at 1000℃ for 3 h:ε_(r)=8.25,Q×f=47616 GHz and τf=9.6 ppm/℃.

关键词： microwave dielectric ceramics BaCuSi_(2)O_(6) Lattice energy

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