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Developing high-Q × f value MgNb_(2–x)Ta_(x)O_(6)(0≤x≤0.8) columbite ceramics and clarifying the impact mechanism of dielectric loss: Crystal structure, Raman vibrations, microstructure, lattice defects, chemical bond characteristics, structural parameters, and microwave dielectric properties in-depth studies

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Journal of Materials Science & Technology 2023年第15期146卷 186-199页

作者： Lingxia Li Yuting Li Jianli Qiao Mingkun Du School of Microelectronics Tianjin UniversityTianjin300072China Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin UniversityTianjin300072China Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology Tianjin UniversityTianjin300072China

With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during propagation.In order to improve the Q×f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties,Ta5+ion is introduced to design and fabricate MgNb_(2-x)Ta_(x)O_(6)(0≤x≤0.8)ceramics by the solid-state reaction method.The single columbite phase and dense structure are observed throughout the entire composition range.All elements(Mg,Nb,Ta,and O)can be detected by X-ray photoelectron spectroscopy.Insights from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2)and Ag(3)modes located at∼905 cm−1 dominate the Raman vibration.In addition,theɛr depends on the polarizability reflected by the C–M equation and Raman shift.Theτf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of[Nb/TaO6].Notably,the crucial factors for the huge improvement of Q×f are clarified deeply,in terms of the lower internal strain,the reduced ordering-induced domain size,and the chemical bond valence closer to the ionic valence state,which promotes the stability of crystal structure.Moreover,the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies,thereby reducing the dielectric loss caused by the conductance.Excellent microwave properties(ɛr=19.2,Q×f=170,000 GHz,andτf=−55.6 ppm℃–1)are achieved in MgNb1.4Ta0.6O6 ceramic,specifically a nearly 40%increase in the Q×f.This work has enriched the theory associated with low dielectric loss and provided the MgNb_(1.4)Ta_(0.6)O_(6) ceramic with a pretty high-Q×f for the application in the design of the 5G/6G wireless communication devices.

关键词： Advances in 5G/6G materials High-Q×f value ceramic Group theoretical analysis Oxygen vacancy Chemical bond characteristics microwave dielectric properties

Enhanced thermal conductivity and microwave dielectric properties by mesostructural design of multiphase nanocomposite

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Nano Materials Science 2022年第2期4卷 133-138页

作者： Liping Zhou Peng Xu Faxiang Qin Institute for Composites Science Innovation(InCSI) School of Materials Science and EngineeringZhejiang University38 Zheda RoadHangzhou310027PR China

Next-generation packaging materials are expected to have higher thermal conductivity,because the heat accumulated in high-performance electronic equipment should be removed to increase the service life of the equipment.At the same time,the dielectric loss of the material needs to be reduced to lessen signal delay and attenuation,especially for the applications under high frequency.In this work,we introduce nano-silicon carbide(SiC)and carbon nanotubes(CNTs)into the polystyrene(PS)and poly(methyl methacrylate)(PMMA)blends system.The design of two-way migration at the interface of CNTs and SiC nanoparticles is realized through the masterbatch method and processing technology control.As a result,the thermal conductivity is successfully increased up to 75%.Meanwhile,compared to the CNTs single-phase migration system,it effectively reduces the dielectric loss of the nanocomposite and optimizes the electrical insulation.This work has significant practical application value in the design of electronic device substrates and packaging materials,and provides an innovative methodology for the mesostructure design of multiphase nanocomposites.

关键词： Immiscible blends Nanocomposite microwave dielectric properties Thermal conductivity

Low-temperature sintering and microwave dielectric properties of CaMg1−xLi2xSi2O6(x=0−0.3)ceramics

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Journal of Advanced Ceramics 2020年第4期9卷 471-480页

作者： Fangyi Huang Hua Su Yuanxun Li Huaiwu Zhang Xiaoli Tang State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu610054China Jiangxi Guo Chuang Industrial Park Development Co. Ltd.Ganzhou341000China

In this study, low-temperature fired CaMg1−xLi2xSi2O6 microwave dielectric ceramics were prepared via the traditional solid-state reaction method. In this process, 0.4 wt% Li2CO3-B2O3-SiO2-CaCO3-Al2O3 (LBSCA) glass was added as a sintering aid. The results showed that ceramics consisted of CaMgSi2O6 as the main phase. The second phases were CaSiO3 always existing and Li2SiO3 occurring at substitution content x > 0.05. Li+ substitution effectively lowered sintering temperature due to 0.4 wt% LBSCA and contributed to grain densification, and the most homogeneous morphology could be observed at x = 0.05. The effects of relative density, the second phase, and ionic polarizability on dielectric constant (εr) were investigated. The quality factor (Q × f) varied with packing fraction that concerned the second phase. Moreover, the temperature coefficient of the resonant frequency (τf) was influenced by MgO6 octahedral distortion and bond valence. Excellent dielectric properties of the CaMg1−xLi2xSi2O6 ceramic was exhibited at x = 0.05 with εr = 7.44, Q × f = 41,017 GHz (f = 15.1638 GHz), and τf = −59.3 ppm/°C when sintered at 900 °C. It had a good application prospect in the field of low-temperature co-fired ceramic (LTCC) substrate and devices.

关键词： low permittivity low-temperature sintering crystal structure microwave dielectric properties

Effect of Sb-site nonstoichiometry on the structure and microwave dielectric properties of Li_(3)Mg_(2)Sb_(1-x)O_(6) ceramics

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Journal of Advanced Ceramics 2020年第5期9卷 588-594页

作者： Cuijin PEI Jingjing TAN Yang LI Guoguang YAO Yanmin JIA Zhaoyu REN Peng LIU Huaiwu ZHANG School of Science Xi’an University of Posts and TelecommunicationsXi’an 710121China School of Physics Northwest UniversityXi’an 710069China College of Physics and Information Technology Shaanxi Normal UniversityXi’an 710062China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054China

The non-stoichiometric Li_(3)Mg_(2)Sb_(1-x)O_(6)(0.05≤x≤0.125)compounds have been prepared via the mixed oxide method.The influences of Sb nonstoichiometry on the sintering behavior,microstructure,phase composition along with microwave dielectric performances for Li_(3)Mg_(2)Sb_(1-x)O_(6) ceramics were studied.Combined with X-ray diffraction(XRD)and Raman spectra,it was confirmed that phase composition could not be affected by the Sb nonstoichiometry and almost pure phase Li_(3)Mg_(2)SbO_(6) was formed in all compositions.Appropriate Sb-deficiency in Li_(3)Mg_(2)SbO_(6) not only lowered its sintering temperature but also remarkably improved its Q×f value.In particular,non-stoichiometric Li_(3)Mg_(2)Sb_(0.9)O_(6) ceramics sintered at 1250℃/5 h owned seldom low dielectric constant ε_(r)=10.8,near-zero resonant frequency temperature coefficient τ_(f)=-8.0 ppm/℃,and high quality factor Q×f=86,300 GHz(at 10.4 GHz).This study provides an alternative approach to ameliorate its dielectric performances for Li_(3)Mg_(2)SbO_(6)-based compounds through defect-engineering.

关键词： microwave dielectric properties ceramics sintering antimony compounds

Influence of(Mg_(1/3)Nb_(2/3))complex substitutions on crystal structures and microwave dielectric properties of Li2TiO3 ceramics with extreme low loss

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Journal of Materiomics 2018年第4期4卷 368-382页

作者： Huan-Huan Guo Di Zhou Li-Xia Pang Jin-Zhan Su Electronic Materials Research Laboratory Key Laboratory of the Ministry of Education&International Center for Dielectric ResearchSchool of Electronic and Information EngineeringXi'an Jiaotong UniversityXi'an710049China Micro-optoelectronic Systems Laboratories Xi'an Technological UniversityXi'an710032ShaanxiChina International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'anShaanxi710049China

A systematic investigation of the Li2Ti1-x(Mg_(1/3)Nb_(2/3))xO_(3)(0.1≤x≤0.35)solid solutions synthesized by traditional solid-state reaction method is reported in this work.In the composition range of 0.1≤x≤0.25,a monoclinic rock salt structured solid solution was formed.When x increased to 0.3,a phase transition from monoclinic to cubic phase,along with an order-disorder phase transition,was observed.With x increased from 0.1 to 0.35,the microwave permittivity(εr)and temperature coefficient of resonant frequency(TCF)of the Li2Ti1-x(Mg_(1/3)Nb_(2/3))xO_(3)ceramics decreased linearly from 21.0 to 18.6,+27.1 to-19.4 ppm/℃,respectively.The Li_(2)Ti_(0.75)(Mg_(1/3)Nb_(2/3))0.25O_(3)ceramic sintered at 1170℃shows high performance of microwave dielectric properties with aεr~19.6,a Qf(Q=quality factor=1/dielectric loss;f=resonant frequency)~109,770 GHz(at 7.7 GHz)and a near zero TCF~t 1.2 ppm/℃.Moreover,the burying sintering process can reduce the volatilization of lithium so that the porosity of Li_(2)Ti_(0.75)(Mg_(1/3)Nb_(2/3))0.25O_(3)ceramic was reduced effectively,which made Li_(2)Ti_(0.75)(Mg_(1/3)Nb_(2/3))0.25O_(3)ceramic promising for future applications.Selected area electron diffraction patterns,high-resolution transmission electron microscopy,Raman and far-infrared spectra were employed to study the relation between crystal structure and microwave dielectric properties in detail.

关键词： microwave dielectric properties Phase evolution Crystal structure High quality

Microstructure and microwave dielectric properties of ZnO-B_2O_3 added (Ca_(0.254)Li_(0.19)Sm_(0.14))TiO_3 ceramics

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Rare Metals 2010年第3期29卷 243-247页

作者： LU Yin LI Haitao LI Qian ZHANG Boping Department of Mechanical Engineering Henan Polytechnic Institute Nanyang 473009 China School of Materials Science and Engineering Henan University of Science and Technology Luoyang 471003 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The effects of ZnO-B2O3 （ZB2） on the sintering behavior and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics were investigated. The densities of the specimens reached the maximum value by adding 3 wt.% ZB2 and then decreased. The sintering temperature of the specimens was lowered from 1300 to 1100℃ without degradation of the microwave dielectric properties. The （Ca0.254Li0.19Sm0.14）TiO3＋ 3 wt.% ZB2 sintered at 1100℃ for 3 h showed good microwave dielectric properties, εr= 108.2, Qf= 6545 GHz, and rf= 6.5 ppm/℃, respectively, indicating that ZB2 was an effective sintering aid to improve the densification and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics.

关键词： microwave dielectric properties densification ceramics sintering behavior

Microstructures and microwave dielectric properties of La-Substituted Ba(Mg_1/3Nb_(2/3))O_3 Ceramics

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Journal of Rare Earths 2005年第S1期23卷 171-174页

作者：田中青韩星余洪滔张津黄伟九 School of Materials Science and Engineering Chongqing Institute of Technology Chongqing 400050 China State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China) State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China School of Materials Science and Engineering Chongqing Institute of Technology Chongqing 400050 China

La substituted Ba(Mg_ 1/3Nb_ 2/3)O_3 ceramics was expected to enhance the 1∶2 ordering degree of B-site ions due to the existence of vacancies that promote cation movement and result in improvement of the Q_f value. The relation between the microstructure and microwave dielectric properties of Ba_ 1-xLa_ 2x/3(Mg_ 1/3Nb_ 2/3)O_3 ceramics was investigated. La substituted Ba(Mg_ 1/3Nb_ 2/3)O_3 ceramics can improve the sinterability of specimens. Both 1:2 ordering degree and grain size increase as A-site vacancies increase. This can be explained by the existence of vacancies that promote cation movement. The Q_f value increase with small La content, then decrease rapidly. The highest Q_f value achieved in this investigation is about 55000 GHz for Ba_ 0.995La_ 0.01/3(Mg_ 1/3Nb_ 2/3)O_3. The improvement of Q_f value with A-site vacancies is related to the increase of the degree of B-site ordering and grain size of the specimen.

关键词： barium magnesium niobate microwave dielectric properties ordering microstructure

Enhanced microwave dielectric properties of wolframite structured Zn_(1-x)Cu_(x)WO_(4) ceramics with low sintering temperature

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Journal of Materiomics 2021年第6期7卷 1309-1317页

作者： Qin Zhang Xiaoli Tang Fangyi Huang Xiaohui Wu Yuanxun Li Hua Su State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu610054China Jiangxi Xingkang Electronic Technology Co LtdGanzhouChina

The crystal structure,Raman vibration,chemical bond characteristics,and microwave dielectric properties of Zn_(1-x)Cu_(x)WO_(4)(x=0-0.15)ceramics prepared by a solid-state reaction were investigated by XRD refinement,Raman spectroscopy,P-V-L theory and XPS.According to the P-V-L theory,the properties of the W-O bond are stronger than those of the Zn-O bond,which makes a major contribution to the dielectric properties.The relative permittivity is mainly affected by the average bond ionicity,and the variations in the dielectric loss and tf are mainly attributed to the lattice energy and bond energy.XPS shows that the presence of Cut could produce oxygen vacancy defects,increasing the dielectric loss.Additionally,Raman spectra show that the increasing molecular polarizability causes the Raman shift to move to a low wavenumber,and the changes in Raman intensity and FWHM lead to a decrease in the degree of short-range ordering.Particularly,Zn_(0.97)Cu_(0.03)WO_(4) ceramics sintered at 925℃ showed satisfactory properties(εr=14.20,tanδ=1.473×10^(-4) at 9.087 GHz,and tf=-40 ppm/℃),which can potentially be applied to LTCC technology and indicate that Cu substitution can not only reduce the sintering temperature,but also optimize the dielectric properties.

关键词： P-V-L theory microwave dielectric properties Raman spectra Zn_(1-x)Cu_(x)WO_(4) XPS

Influence of CaxSr1-x(0≤x≤1)Substitution for Zn on microwave dielectric properties of Li2ZnTi3O8 Ceramic as Temperature Stable Materials

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Journal of Wuhan University of Technology(Materials Science) 2020年第4期35卷 686-690页

作者：田仕 LIAO Zelin WANG Heng 王为民 School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China School of Materials Science and Engineering Wuhan Institute of TechnologyWuhan 430205China Stat Key Laboratory of Advanced Technology for Materials Synthesisand Processing Wuhan University of TechnologyWuhan 430070China

A temperature stable Li2Zn0.95(SrxCa1-x)0.05Ti3O8(0≤x≤1)ceramics were fabricated using a conventional solid-state route sintered at 1100℃for 4 h.The XRD results indicate that the main phase Li2ZnTi3O8 and secondary phase including SrxCa1-xTiO3(0≤x≤1)solid solution and TiO2 co-exist in composite and form a stable composite system when the(CaxSr1-x)(0≤x≤1)substitutes for Zn of Li2ZnTi3O8 ceramic.As x is increased from 0 to 1,the relative permittivity(εr)increases from 26.65 to 27.12,and the quality factor(Q×f)increases from 63300 to 66600 GHz.With the increased of x,the temperature coefficient of resonant frequency(τf)increases from 0.27 to 8.23 ppm/℃,and then decreases to 3.51 ppm/℃.On the whole,the Li2Zn0.95(SrxCa1-x)0.05Ti3O8(0≤x≤1)ceramics show excellent comprehensive properties of middleεr=25-27,higher Q×f≥60000 GHz andτf≤±8.5 ppm/℃.

关键词： Li2Zn0.95(SrxCa1-x)0.05Ti3O8(0≤x≤1) microwave dielectric properties temperature stable materials substitution