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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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作者 Guoqiang He Yu Jiang +9 位作者 Kaixin Song Yanjun Liu Yuan Nie Wenjie Zhang Ziqi Zhao Yinghan He Xinyue Ma Xiuli Chen Xu Li Huanfu Zhou 《Journal of Advanced Ceramics》 SCIE EI CAS CSCD 2024年第2期155-165,共11页
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 ... 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. 展开更多
关键词 millimeter wave microwave dielectric ceramics dielectric resonator antenna nonstoichiometric ratio
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Probing atomic-scale structure of dielectric ceramics with scanning transmission electron microscopy
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作者 Min Zhang Rui Wei +1 位作者 Jinquan Zeng Yuan-Hua Lin 《Journal of Advanced Dielectrics》 2024年第3期1-10,共10页
High performance dielectric capacitors are ubiquitous components in the modern electronics industry,owing to the highest power density,fastest charge-discharge rates,and long lifetime.However,the wide application of d... High performance dielectric capacitors are ubiquitous components in the modern electronics industry,owing to the highest power density,fastest charge-discharge rates,and long lifetime.However,the wide application of dielectric capacitors is limited owing to the low energy density.Over the past decades,multiscale structures of dielectric ceramics have been extensively explored and many exciting developments have been achieved.Despite the rapid development of energy storage properties,the atomic structure of dielectric materials is rarely investigated.In this paper,we present a brief overview of how scanning transmission electron microscopy(STEM)is used as a tool to elucidate the morphology,local structure heterogeneity,atomic resolution structure phase evolution and the correlation with energy storage properties,which provides a powerful tool for rational design and synergistic optimization. 展开更多
关键词 Atomic-scale structure dielectric ceramics STEM energy storage
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Ultrahigh energy storage with superfast charge-discharge capability achieved in linear dielectric ceramic
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作者 Xuqing Zhang Yongping Pu +3 位作者 Yating Ning Lei Zhang Bo Wang Zhemin Chen 《Journal of Materials Science & Technology》 SCIE EI CAS 2024年第10期59-67,共9页
Ceramic capacitors designed for energy storage demand both high energy density and efficiency.Achiev-ing a high breakdown strength based on linear dielectrics is of utmost importance.In this study,we present the remar... Ceramic capacitors designed for energy storage demand both high energy density and efficiency.Achiev-ing a high breakdown strength based on linear dielectrics is of utmost importance.In this study,we present the remarkable performance of densely sintered(1-x)(Ca_(0.5)Sr_(0.5)TiO_(3))-xBa4Sm28/3Ti18O54 ceramics as energy storage materials,with a measured energy density(Wrec)of 4.9 J/cm^(3)and an ultra-high ef-ficiency(η)of 95%which is almost optimal in linear dielectric that has been reported.To unravel the underlying mechanisms,we conducted a systematic investigation on the influence of adding paraelec-tric Ba_(4)Sm_(28/3)Ti_(18)O_(54)(BST)on both microstructure and macroscopic electrical properties of Ca_(0.5)Sr_(0.5)TiO_(3)(CST).Notably,the addition of BST effectively reduces the grain size of CST.The conduction mechanism is primarily governed by grain boundaries,where high-density grain boundaries act as barriers to charge carrier transport due to their elevated resistivity.Moreover,the activation energy associated with grain boundaries increases with rising resistivity,implying a lower concentration of free vacancies within these regions.The increased barrier height for oxygen vacancy migration at grain boundaries compensates for the grain boundary defects,thereby resulting in enhanced breakdown strength.This characteristic offers a substantial advantage in terms of thermal and frequency stability(25-175℃,1-100 Hz).This work introduces a candidate material with outstanding comprehensive energy storage properties. 展开更多
关键词 Linear dielectric ceramic Ca0.5 Sr0.5 TiO3 Energy storage Grain boundary
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Improved microwave dielectric properties of MgAl_(2)O_(4)spinel ceramics through(Li_(1/3)Ti_(2/3))^(3+)doping 被引量:1
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作者 李潇 杨习志 +7 位作者 赖元明 张芹 李宝阳 戚聪 殷俊 王凡硕 巫崇胜 苏桦 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第5期668-673,共6页
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,micros... 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. 展开更多
关键词 microwave dielectric ceramics MgAl_(2)O_(4)ceramic co-substitution MgTi_(2)O_(5) solid solubility limit
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The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams 被引量:9
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作者 Hongcheng YANG Shuren ZHANG +5 位作者 Hongyu YANG Qingyu WEN Qiu YANG Ling GUI Qian ZHAO Enzhu LI 《Journal of Advanced Ceramics》 SCIE CAS CSCD 2021年第5期885-932,共48页
The explosive process of 5G communication evokes the urgent demand of miniaturized and integrated dielectric ceramics filter It is a pressing need to advance the development of dielectric ceramics utilization of emerg... The explosive process of 5G communication evokes the urgent demand of miniaturized and integrated dielectric ceramics filter It is a pressing need to advance the development of dielectric ceramics utilization of emerging technology to design new materials and understand the polarization mechanism.This review provides the summary of the study of microwave dielectric ceramics(MWDCs)sintered higher than 1000℃ from 2010 up to now,with the purpose of taking a broad and historical view of these ceramics and illustrating research directions.To date,researchers endeavor to explain the structure-property relationship of ceramics with multitude of approaches and design a new formula or strategy to obtain excellent microwave dielectric properties.There are variety of factors that impact the permittivity,dielectric loss,and temperature stability of dielectric materials,covering intrinsic and extrinsic factors.Many of these factors are often intertwined,which can complicate new dielectric material discovery and the mechanism investigation.Because of the various ceramics systems,pseudo phase diagram was used to classify the dielectric materials based on the composition.In this review,the ceramics were firstly divided into ternary systems,and then brief description of the experimental probes and complementary theoretical methods that have been used to discern the intrinsic polarization mechanisms and the origin of intrinsic loss was mentioned.Finally,some perspectives on the future outlook for high-temperature MWDCs were offered based on the synthesis method,characterization techniques,and significant theory developments. 展开更多
关键词 high-temperature microwave dielectric ceramics(MWDCs) pseudo phase diagram developments and challenges composition-structure-property relationship
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Machine learning approaches for permittivity prediction and rational design of microwave dielectric ceramics 被引量:3
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作者 Jincheng Qin Zhifu Liu +1 位作者 Mingsheng Ma Yongxiang Li 《Journal of Materiomics》 SCIE EI 2021年第6期1284-1293,共10页
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 pract... 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. 展开更多
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 被引量:3
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作者 Wen Bin Hong Lei Li +3 位作者 Han Yan Shu Ya Wu Hang Sheng Yang Xiang Ming Chen 《Journal of Materiomics》 SCIE EI 2020年第2期233-239,共7页
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... 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. 展开更多
关键词 Boric acid Microwave dielectric ceramics Room-temperature cold sintering Ultra-low permittivity
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Recent progress of ecofriendly perovskite-type dielectric ceramics for energy storage applications 被引量:2
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作者 Feng Li Jiwei Zhai +1 位作者 Bo Shen Huarong Zeng 《Journal of Advanced Dielectrics》 CAS 2018年第6期43-60,共18页
Increasing concern has been focused on the search for ecofriendly dielectric ceramics to meet the extensive demands of pulsed capacitors.Due to the advantages of high-energy storage density,efficiency,and excellent te... Increasing concern has been focused on the search for ecofriendly dielectric ceramics to meet the extensive demands of pulsed capacitors.Due to the advantages of high-energy storage density,efficiency,and excellent temperature stability,optimization of energy storage performance in dielectric ceramics has been a goal in the past decades.This review summarizes the recently reported progress in energy storage properties of typical perovskite-type lead-free ceramics.The advantages and shortcomings in the various kinds of ceramics are discussed.Finally,future prospects are presented to provide some guidelines for the exploration of new materials. 展开更多
关键词 LEAD-FREE dielectric ceramics energy storage charge-discharge perovskite-type.
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Ultralow-loss (1-x)CaWO_(4)-xNa_(2)WO_(4) (x=0.1,0.2) microwave dielectric ceramic for LTCC applications 被引量:2
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作者 Tao Sun Bin Xiao +5 位作者 Fei Jin` Xinwei Xu Feng Wang Naichao Chen Xianqiang Chen Hong Wang 《Journal of Materiomics》 SCIE EI 2021年第5期1022-1028,共7页
In this work,the(1-x)CaWO_(4)-xNa_(2)WO_(4)(x=0.1,0.2,denoted as 0.9CW-0.1NW and 0.8CW-0.2NW,respectively)ultralow-loss microwave dielectric ceramics were prepared via solid-state reaction method.Using low melting-poi... In this work,the(1-x)CaWO_(4)-xNa_(2)WO_(4)(x=0.1,0.2,denoted as 0.9CW-0.1NW and 0.8CW-0.2NW,respectively)ultralow-loss microwave dielectric ceramics were prepared via solid-state reaction method.Using low melting-point Na_(2)WO_(4) as sintering aid to prepare CaW_(O4)eNa_(2)WO_(4) composite ceramics,the sintering temperature of CaWO_(4) was successfully reduced while maintaining excellent microwave performance.The optimal microwave dielectric properties have been achieved at 900C for 0.9CW-0.1NW ceramic:εr=9.0,Q×f=105660 GHz,tandδ=1.1×10^(-4)and tf=35.4 ppm/℃ at a frequency of 12.0 GHz.For the 0.8CW-0.2NW ceramic,the optimal microwave dielectric properties have been obtained at 740C,withεr=8.5,Q×f=97014 GHz,tandδ=1.2×10^(-4)and tf=37.4 ppm/℃ at a frequency of 11.8 GHz.In summary,both composite ceramics exhibit low sintering temperatures,excellent dielectric properties and chemical compatibility with the Ag electrode.The findings of this study provide an effective approach to prepare novel composite ceramics as promising candidates for LTCC applications. 展开更多
关键词 Ultralow-loss LTCC Raman spectra Microwave dielectric ceramics
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Dielectric Properties and Defect Structure of Bi-doped SrTiO_3 Ceramics 被引量:1
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作者 HUANG Min, ZHAO Wei-zhong(Dept. of Phys., Zhejiang University, Huangzhou 310027, CHN) 《Semiconductor Photonics and Technology》 CAS 2001年第1期24-29,共6页
The dielectric properties of ceramics with composition of (Sr 1-x Bi x )TiO 3+x/2 (where x =0.05~0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr 1-x... The dielectric properties of ceramics with composition of (Sr 1-x Bi x )TiO 3+x/2 (where x =0.05~0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr 1-x Bi x )TiO 3+x/2 system are greatly varied with an increase of the stoichiometric amounts of Bi 2O 3. The relative permittivity of the solid solutions is high, and the dissipation factor is low. The positron annihilation technique(PAT) was adopted to study the defect structure. An explanation of the dielectric properties of Bi-doped SrTiO 3 ceramics has been suggested in terms of electron-compensation and vacancy or defect-compensation mechanisms and space-charge polarization mechanism. 展开更多
关键词 dielectric ceramics Defect structure Positron annihilation
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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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作者 王浩 陈文 刘涛 《Journal of Rare Earths》 SCIE EI CAS CSCD 2005年第1期32-35,共4页
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 v... 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. 展开更多
关键词 inorganic nonmetallic materials PEROVSKITE microwave dielectric ceramics dielectric properties rare earths
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Effect of La^(3+), Sr^(2+) on Microwave Dielectric Properties of CaO-MgO-Nb_2O_5^-TiO_2 System Ceramics
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作者 Wang Hao Chen Wen Tian Zhongqing 《Journal of Rare Earths》 SCIE EI CAS CSCD 2006年第1期80-80,共1页
The effect of La^3 + , Sr^2+ on the microstructure and microwave properties of CaO-MgO-Nb2O5-TiO2 system ceramics was investigated. The result shows that a single complex perovskite structure formed within investiga... The effect of La^3 + , Sr^2+ on the microstructure and microwave properties of CaO-MgO-Nb2O5-TiO2 system ceramics was investigated. The result shows that a single complex perovskite structure formed within investigated composition range in La^3+ , Sr2-doped CaO-MgO-Nb2O5-TiO2 system ceramics. With increasing of La^3+ , Sr^2+ content, the structure of La^3+ , Sr2-doped CaO-MgO-Nb2O5-TiO2 system ceramic respectively maintain orthorhombic type. 展开更多
关键词 inorganic nonmetallic materials PEROVSKITE microwave dielectric ceramics dielectric properties rare earths
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Study on the dielectric properties of Mg-doped NaBiTi6O14 ceramics
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作者 陈勇 薛思敏 +6 位作者 骆迁 苏虎音 陈琪 黄镇 徐玲芳 曹万强 黄兆祥 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第4期462-467,共6页
With the interest in using lead-free materials to replace lead-containing materials increasing,the use of Na_(0.5)Bi_(0.5)TiO_3(NBT) has come into our sight.We studied the composition of NBT and found that NaBiT... With the interest in using lead-free materials to replace lead-containing materials increasing,the use of Na_(0.5)Bi_(0.5)TiO_3(NBT) has come into our sight.We studied the composition of NBT and found that NaBiTi_6O_(14) ceramics can be compositionally tuned by Mg-doping on the Ti-site to optimize the dielectric properties.In this study,Mg-doped NaBiTi_6O_(14)(NaBi(Ti_(0.98)Mg_(0.02))_60_(14-d)) ceramics were prepared by a conventional mixed oxide route at different sintering temperatures,and their dielectric properties have been studied at a wide temperature range.X-ray diffraction(XRD) patterns of the NBT-based ceramics indicate that all samples have a pure phase without any secondary impurity phase.The experimental data show that after Mg-doping,the relative permittivity and dielectric loss become lower at 1040,1060,and1080 ℃ except 1020 ℃ and at different frequencies from 10 kHz,100 kHz to 1 MHz.Take 1060 ℃ for example,when the sintering temperature is 1060 ℃ at 1 MHz,the minimum relative permittivity of NaBiTi_6O_(14) is 32.9 and the minimum dielectric loss is 0.01417,the relative permittivity of NaBi(Ti_(0.98)Mg_(0.02))_60_(14-δ) under the same condition is 25.8 and the dielectric loss is 0.000104.We explored the mechanism of Mg-doping and surprisingly found that the dielectric property of NaBi(Ti_(0.98)Mg_(0.02))_60_(14-δ) becomes better owing to Mg-doping.Thus,NaBi(Ti_(0.98)Mg_(0.02))_60_(14-δ) can be used in microwave ceramics and applied to new energy materials. 展开更多
关键词 NaBiTi6O14 PERMITTIVITY loss(tanδ) dielectric ceramics
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Structural and Dielectric Properties of Y_2O_3-Doped Ba_(0.92)Sr_(0.08)Ti_(0.95)Sn_(0.05)O_3 Ceramics
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作者 王晓凤 曲远方 李远亮 《Transactions of Tianjin University》 EI CAS 2009年第6期428-433,共6页
The structural and dielectric properties of Ba0.92Sr0.08Ti0.95Sn0.0503 (BSTS) +x(molar ratio, %) Y^3+ceramics are investigated. Combining the lattice parameters and the distortion of crystal lattice, an alternat... The structural and dielectric properties of Ba0.92Sr0.08Ti0.95Sn0.0503 (BSTS) +x(molar ratio, %) Y^3+ceramics are investigated. Combining the lattice parameters and the distortion of crystal lattice, an alternation of substitution preference of Y^3+ ion for the host cations in perovskite lattice is found. Owing to Y^3- ion entering the A site, the maximum dielectric constant is 5 627 for 1.25% Y^3+-doped samples; when Y^3- ion is more than 1.25%, it tends to occupy the B site in perovskite lattice, causing a drop in the dielectric constant. Owing to the appearance of oxygen vacancy, the optimized dielectric loss is 0.004 for 1.25% Y^3+-doped samples. The thermal stability of BSTS ceramics is significantly improved and the Curie temperature shifts to lower value with the amount of Y2O3 increased, making it a superior candidate for capacitor applications. 展开更多
关键词 dielectric ceramics Y^3+-doping microstructure dielectric properties
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Effect of Rare Earth Oxides on the Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb_2O_5-TiO_2 System Ceramics
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作者 王浩 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2005年第4期83-86,共4页
La2O3 and SrO-doped CaO-MgO-Nb2O3-TiO2 system ceramics were prepared by solid-state ceramic technique.The microstructure and microwave dielectric properties of CaO-MgO-Nb2O5-TiO2-La2O3 cermics can be adjusted by varyi... La2O3 and SrO-doped CaO-MgO-Nb2O3-TiO2 system ceramics were prepared by solid-state ceramic technique.The microstructure and microwave dielectric properties of CaO-MgO-Nb2O5-TiO2-La2O3 cermics can be adjusted by varying the amount of La^3+ or Sr^2+ ions respectively.The replacement of Ca^2+ by La^3+ at A-site of the ceramics increases the quality factor Q value( at 7.6GHz)as well as the temperature coefficient of resonant frequency τf and decreases the dielectric constant εr and the substitution of Sr^2+ at A-site in this ceramics system exhibits opposite characteristics.The microwave properties of La^3+,Sr^2+-doped CaO-MgO-Nb2O5-TiO2 system ceramics depend on the degree of octahedral distortion inside materials. 展开更多
关键词 PEROVSKITE microwave dielectric ceramic dielectric properties
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SPONTANEOUS POLARIZATION IN UNCONVENTIONAL Ta_(2)O_(5)DIELECTRIC CERAMICS BY LASER SINTERING
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作者 LINGFEI JI YIJIAN JIANG 《Journal of Advanced Dielectrics》 CAS 2011年第2期197-201,共5页
Spontaneous polarization was found in Ta_(2)O_(5)dielectric ceramics prepared by laser sintering techmique.After heat corrosion,90°and 180°domains in the ceramics was observed by field emission scanning elec... Spontaneous polarization was found in Ta_(2)O_(5)dielectric ceramics prepared by laser sintering techmique.After heat corrosion,90°and 180°domains in the ceramics was observed by field emission scanning electron micrographs.The crystal structure of the laser-si ntered ceramics at RT was determined as monocinic phase,which indicates the lattice distortion existed in the ceramics.The variation of O-Ta-O bending vibration mode was deduced from the variation of phonon mode at the low wave-mumber(57 cm^(-1)and 250cm^(-1)).The enhancement of effective electric field for tantalum atoms due to the lattice distortion was determined by calculation of charge distribution cofficients.The distortion of crystal structure due to the phase transformation from higher symmetric orthorhombic phase to lower symmetric monoclinic phase expl ained spontaneous polarization in the laser-sintered Ta_(2)O_(5)ceramics. 展开更多
关键词 Spontaneous polarization tantalum-pentoxide DOMAIN dielectric ceramic
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Dielectric Properties of Unfilled Tetragonal Tungsten Bronze Ba4PrFe(0.5)Nb(9.5)O(30) Ceramics 被引量:1
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作者 胡长征 ZHU Qihua +3 位作者 SUN Zhen GUO Zhe LIU Laijun FANG Liang 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2017年第4期904-909,共6页
In order to found new dielectrics ceramics in tungsten bronze structure, unfilled tungsten bronze(TB) ceramics with nominal formula Ba4PrFe(0.5)Nb(9.5)O(30) were prepared by the solid state reaction method. Th... In order to found new dielectrics ceramics in tungsten bronze structure, unfilled tungsten bronze(TB) ceramics with nominal formula Ba4PrFe(0.5)Nb(9.5)O(30) were prepared by the solid state reaction method. The microstructure and dielectric properties were studied using powder X-ray diffraction, field emission scanning electron microscope, and variable temperature dielectric test system. The results show that the ceramics have a single phase and belong to the space group of P4bm with the cell of a = b = 12.4839(3) ?, c = 3.9409(5) ?, V = 614.192(2) ?3. The frequency dependent dielectrics properties show that the ceramics have a Debye-like relaxation at room temperature, while the temperature dependent dielectrics properties indicate that the ceramics are a relaxor and the relaxation is due to the nanopolars and oxygen vacancies. The ceramics have a potential application in electronic ceramics as temperature-stable multilayer ceramic capacitors. 展开更多
关键词 unfilled tetragonal tungsten bronze dielectric properties ceramic
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Dielectric Characteristics in BiFeO3-Modified SrTiO3 Incipient Ferroelectric Ceramics 被引量:1
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作者 刘娟 覃莹 +1 位作者 刘小强 陈湘明 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第2期86-90,共5页
We investigate the dielectric and ferroelectric properties of Sr1-xBixTi1-xFex03 solid solutions (x =0, 0.05, 0.1, 0.15 and 0.2) together with their structures. Through the analysis of Rietveld refinement of powder ... We investigate the dielectric and ferroelectric properties of Sr1-xBixTi1-xFex03 solid solutions (x =0, 0.05, 0.1, 0.15 and 0.2) together with their structures. Through the analysis of Rietveld refinement of powder x-ray diffraction, a cubic structure in space group Pm3m is determined for all the compositions. An obvious dielectric relaxation peak differing from SrTiO3 is observed in the present ceramics. The peak temperature Tm increases with increasing x, and it approaches room temperature at x =0.2. The Vogel Fulcher law and Curie Weiss law fittings further confirm the relaxor ferroelectricity in the present ceramics. 展开更多
关键词 FE TI dielectric Characteristics in BiFeO3-Modified SrTiO3 Incipient Ferroelectric ceramics
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Dielectric and Magnetic Properties of (1-x)CaTiO3-xNi0.5Zn0.5Fe2O4 Composite Ceramics
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作者 陈晨 刘银 +3 位作者 WANG Chuanchuang ZHU Yanyan CHENG Qian YI Zhiguo 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2016年第4期786-790,共5页
(1-x)CaTiO3-xNi0.5Zn0.5Fe2O4(0 x 1.0) composite ceramics were synthesized by a conventional solid state reaction method.The phase formation,microstructure,and dielectric and magnetic properties were investigated b... (1-x)CaTiO3-xNi0.5Zn0.5Fe2O4(0 x 1.0) composite ceramics were synthesized by a conventional solid state reaction method.The phase formation,microstructure,and dielectric and magnetic properties were investigated by X-ray diffraction,scanning electron microscopy,precision impedance analysis,and vibrating sample magnetometry,respectively.The results indicate that the composite ceramics are composed of both perovskite phase Ca TiO3 and spinel phase Ni0.5Zn0.5Fe2O4.The maximal relative density for 0.5CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics reaches 97.8%,as it has been sintered at the temperature of 1260 ℃ for 3 h.Dielectric constant and loss tangent of(1-x)CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics show dispersion in the low frequency range.Their phase transition temperature of the dielectric constant shifts to lower temperatures with the increase of Ni0.5Zn0.5Fe2O4 content.This phenomenon is attributed to that the phase transition temperature of CaTiO3 is higher than that of Ni0.5Zn0.5Fe2O4.The saturation magnetization of (1-x)CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics increases with the Ni0.5Zn0.5Fe2O4 ferrite content. 展开更多
关键词 ceramics dielectric sintered magnetization vibrating impedance saturation attributed tangent perovskite
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Lattice evolution, order transformation, and microwave dielectric properties of the Zn_(1-x)Li_(2x)TiO_(3)(0≤x≤1) system ceramics
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作者 Qianbiao Du Longxiang Jjang +3 位作者 Linzhao Ma Jjanhong Duan Zeyan Zhou Hao Li 《Journal of Advanced Ceramics》 SCIE EI CAS CSCD 2024年第8期1178-1188,共11页
Research on doping modification of ZnTiO_(3) ceramics to enhance microwave dielectric properties has been hindered by poor performance,unclear structure-function mechanisms.To expand the applicability of ZnTiO_(3) cer... Research on doping modification of ZnTiO_(3) ceramics to enhance microwave dielectric properties has been hindered by poor performance,unclear structure-function mechanisms.To expand the applicability of ZnTiO_(3) ceramics,this study explores Zn_(1-x)Li_(2x)TiO_(3)(O≤×≤1)ceramics using a phase engineering strategy.Our findings reveal that the introduction of Lit into the ZnTiO_(3) system initiates a multiple phase transition,starting at x=0.1.Initially,ilmenite ZnTiO_(3) transforms into a cubic ordered spinel phase(space group P4332).Subsequently,a transition to a disordered spinel phase(space group Fd3m)occurs at x=0.5,culminating in the formation of a monoclinic rock salt-structured LizTiO3 phase.Significantly,two sets of ceramics with near-zero temperature coefficients of resonance frequency(t:)were obtained at x=0.1 and 0.75.Moreover,the quality factor(Qxf)demonstrated a 4.4-fold increase compared to that of ZnTiO_(3) ceramics at x=0.25(105,013 GHz).Additionally,it was observed that the Ti4 polarization in Zn_(1-x)Li_(2x)TiO_(3) ceramics was underestimated by 11.3%-13.3%,causing the measured dielectric constant(e.)exceeding the theoretical dielectric constant(eth).The ionic polarizability of Ti*was adjusted to stabilize around 3.29 A.Evaluation using multiple methods,including Phillips-van Vechten-Levine(P-V-L)theory,Raman vibrational mode analysis,bond valence,bond energy theory,and octahedral distortion,confirms that the Ti-O bonds within the octahedron predominantly affect&r,the increasing lattice energy(U)contributes to the enhancement of Qxf,and the strengthened Li-O bond energy effectively regulates Tr. 展开更多
关键词 microwave dielectric ceramics phase transitions Phillips-van Vechten-Levine(P-V-L) Zn_(1-x)Li_(2x)TiO_(3)
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