Co取代对Nd(Zn0.5Ti0.5)O3微波介质陶瓷结构与性能的影响

采用传统固相法制备Nd[(Zn1?xCox)0.5Ti0.5]O3 (0≤x≤0.9)微波介质陶瓷,研究Co2+在B位取代Zn2+对Nd(Zn0.5Ti0.5)O3微波介质陶瓷的结构和微波介电性能的影响. 结果表明,在研究的组分范围内,Nd[(Zn1?xCox)0.5Ti0.5]O3陶瓷均能形成单斜钙钛矿型固溶体,随Co取代量增加,陶瓷的相对介电常数?r逐渐减小,谐振频率温度系数?f逐渐向负值移动,品质因数Q×f先增大后下降,在x=0.3 mol时达到最大值215130 GHz, Q×f大幅增加是有序度作用所致. 在1410℃下烧结4 h, Nd[(Zn0.7Co0.3)0.5Ti0.5]O3陶瓷具有优异的微波介电性能,?r=31.2, Q×f=215130 GHz, ?f=?35.7×10?6℃?1.     

Sm2O3掺杂的Bi2O3-ZnO-Nb2O5基陶瓷的烧结特性与介电性能

用传统的固相法合成了Sm2O3掺杂的Bi2O3-ZnO-Nb2O5(BZN)基陶瓷(Bi1.5-xSmxZn0.5)(Zn0.5Nb1.5)O7(0≤x≤0.6,BSZN),通过XRD、AV2782阻抗分析仪等测试手段对其烧结行为、相结构及介电性能进行了系统研究.结果表明纯BZN陶瓷的结构为立方焦绿石单相;当Sm2O3掺杂量较少(0＜x≤0.5)时,样品的相结构仍然保持立方焦绿石单相;随着Sm2O3掺杂量的进一步增加(x≥0.6),样品出现其它相.同时,试样的介电性能随结构的变化而呈现有规律的变化.     

Ba(Mg1/3Nb2/3)O3-Mg4Nb2O9复相陶瓷微波介电性能研究

采用传统固相法制备了(1?x)Ba(Mg1/3Nb2/3)O3?xMg4Nb2O9 [(1?x)BMN?xM4N2,x = 0.003 ~ 0.125] 微波介质陶瓷,研究了相结构、烧结性能与介电性能随 x 的变化规律。结果表明： BMN 与 M4N2 可以两相共存,且二者间存在有限固溶,BMN 的烧结温度及高温稳定性有所降 低。随着 x 的增大,介电常数 εr和谐振频率温度系数 τf逐渐减小,Q × f 值的变化易受到 BMN 有序参数 S 的影响,高度 1:2 有序的 x = 0.026 陶瓷获得了最大 Q × f 值 125000 GHz。综合来看, 在 1320°C 下保温 4 h 烧结的 x = 0.125 样品表现出最佳的微波介电性能：εr = 26.6,Q × f = 111000 GHz,τf = 5 ppm/ºC。     

Pb0.45Ca0.55(Fe0.5Nb0.5)0.9(Sn1-xZrx)O3微波陶瓷介电性能的研究

研究了B位Zr、Sn共掺杂对PCFN微波陶瓷相组成及介电性能的影响.发现总掺杂量为10mol%、Zr/Sn为11时,样品中出现了未知第二相.当Zr/Sn＜1时,样品的Q×f值随Zr含量的增加而降低,谐振频率温度系数随Zr含量的增加而增大;当Zr/Sn＞1时,样品的Q×f值随Zr含量的增加而增大,谐振频率温度系数随Zr含量的增加而降低.     

Al2O3陶瓷微波介电性能的研究与进展

近年来随着微波通讯技术与微波集成电路(microwave integrate circuits,MICs)的发展,用于移动通讯、智能运输系统(Intelligent transport system,ITS)、GPS天线的低介电常数低介电损耗的微波介质陶瓷引起了广泛的关注,其中最具代表性的即为Al2O3陶瓷.本文总结了近几年Al2O3陶瓷微波介电性能的研究情况,系统介绍了Al2O3陶瓷微波介电性能的影响因素和目前研究的Al2O3陶瓷体系,希望对于研究Al2O3陶瓷的微波介电性能提供有益的参考,使其在微波通讯等方面得到更广泛的应用.     

(Mg4-xLi2x)(Nb1.92V0.08)O9陶瓷微波介电性能

采用固相合成法制备了(Mg_(4-x)Li_(2x))(Nb_(1.92)V_(0.08))O_9系列微波介质陶瓷。通过XRD、SEM以及HP网络分析仪等测试手段对其烧结特性、晶体结构和微波介电性能进行了系统研究。结果表明:x<0.3时形成了(Mg_(4-x)Li_(2x))(Nb_(1.92)V_(0.08))O_9固溶体;x≥0.3时,除主相(Mg_(4-x)Li_(2x))(Nb_(1.92)V_(0.08))O_9外,还有少量第二相Li3Mg2NbO6生成。微波介电常数ε随x的增大持续升高,品质因数Q则先增大后减小。x=0.2,950℃,5h烧结样品的微波介电性能达到最佳:ε=12.7,Q.f=14078GHz(f0=8GHz)。     

ZnO-B2O3-Na2O玻璃对Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ陶瓷微波介电性能的影响

研究了ZnO-B2O3-Na2O(ZBN)玻璃对陶瓷的烧结性能及微波介电特性的影响.研究表明ZBN的掺入能有效降低对Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ陶瓷体系的烧结温度150～230 ℃,谐振频率温度系数随ZBN掺入量增加及烧结温度的提高,由负值向正值方向增大.在990 ℃,掺入3%(质量分数,下同)的ZBN,陶瓷微波介电性能最佳:εr=31.5,Qf=12530 GHz,τf =-7.6 ppm/℃.     

CaTiO3添加剂对氧化铝陶瓷烧结、显微结构及微波介电性能的影响

CaTiO3添加剂通过湿法球磨与Al2O3粉料混合,并通过无压烧结制备了氧化铝陶瓷,研究了CaTiO3添加剂对氧化铝陶瓷烧结性能、相组成、显微结构和微波介电性能的影响.CaTiO3可以使Al2O3的烧结温度降低至1450℃,但在该温度下烧结的样品由于CaTiO3的加入会产生CaAl12O19第二相.样品中存在大、小两种晶粒,根据EDS能谱分析,大晶粒主要是CaAl12O19,而小晶粒为Al2O3和CaAl12O19的混合相.添加CaTiO3有利于Al2O3陶瓷介电常数的提高,1450℃下掺杂2.5wt％ CaTiO3的氧化铝陶瓷具有较好的烧结性能和微波介电性能,相对密度可达到97.74％,εr～10.86,Q×f～ 8061 GHz.     

0.7CaTiO3-0.3Sm1-xAlO3陶瓷微波介电性能研究

采用固相反应法制备了0.7CaTiO3-0.3Sm1-xAlO3(CTSA,0≤x≤0.1)微波介质陶瓷,研究了Sm缺位对CTSA陶瓷的晶体结构、微观形貌以及微波介电性能的影响。结果表明,制备的CTSA陶瓷均为正交钙钛矿结构。少量的Sm缺位能够降低CTSA陶瓷的烧结温度,晶粒尺寸增加,同时气孔率增大,陶瓷的Q×f值也有显著提升。当x=0.025、烧结温度为1450℃时,CTSA陶瓷具有最佳微波介电性能:εr=45.2,Q×f=47280GHz和τf=+4.8 ppm/℃。     

烧结温度对LaCrO3陶瓷介电性能的影响

采用La_2O_3和Cr_2O_3为原料,固相法制备了LaCrO_3陶瓷粉末,并在不同烧结温度下得到LaCrO_3陶瓷,通过X射线衍射分析仪、扫描电镜及介电频谱仪对其物相、微结构及介电性能进行了研究。结果表明:1 200℃烧结4 h,LaCrO_3陶瓷的致密度最佳,其颗粒尺寸约为1μm～2μm。随着烧结温度增加,LaCrO_3陶瓷的介电常数和介电损耗随频率增大而减小,这可能归因于纯LaCrO_3陶瓷中的氧空位难以形成,氧空位数非常少。     

Dielectric and impedance spectroscopy of Sr(Bi0.5Nb0.5)O3 ceramics

A lead free polycrystalline material Sr(Bi_0.5Nb_0.5)O₃ was prepared using a high-temperature solid-state reaction technique. Preliminary X-rays diffraction studies exhibit the formation of a single-phase compound in the orthorhombic crystal system. The study of microstructure of gold-coated pellet by scanning electron microscopy (SEM) shows well-defined and homogeneous distribution of grains on the surface of the sample. Detailed studies of dielectric parameters (i.e., ε_r and tan δ) of the compound as a function of temperature at selected frequencies reveal that the values of these parameters are almost independent of temperature. Studies of impedance and related parameters exhibit that these electrical properties of the material are strongly dependent on temperature, and bear a good correlation with the microstructure of the material. The decrease in value of bulk resistance on increasing temperature suggests the existence of negative temperature co-efficient of resistance (NTCR) in the material. Studies of electric modulus show the presence of hopping conduction mechanism in the material with non-exponential-type of relaxation. The nature of variation of dc conductivity with temperature confirms the Arrhenius- and NTCR- types of behaviors of the material. The ac conductivity spectrum provides a typical-signature of an ionic conducting system, and is found to obey Jonscher′s universal power law.     

Dielectric behaviors of Ba(Mg1/3Nb2/3)O3 modified (Na0.5K0.5)NbO3 ceramics

The effects of Ba(Mg_1/3Nb_2/3)O₃ additives to lead-free (1-x)(Na_0.5K_0.5)NbO₃-xBa(Mg_1/3Nb_2/3)O₃ ceramics have been investigated. XRD patterns, SEM images and Raman spectra have been used to discuss phase structure transitions and microstructure. The dielectric behavior has been also investigated by using the empirical law, the Curie-Weiss law and the spin-glass model. Results show the diffused phase transition behavior to be enhanced by increasing Ba(Mg_1/3Nb_2/3)O₃ addition and the dielectric behavior to be changed to the more short range order of relaxor ferroelectric. Barium and Magnesium cations are suggested to enter into the cation sites and induce the changes of lattice structure, microstructure, compositional fluctuation, cation disorder and correlation of neighboring cluster-sized moments.     

Synthesis, Sintering, and Microwave Dielectric Properties of KTaO3 Ceramics

Studies of a synthesis of KTaO₃ displayed a two-step reaction path with the intermediate formation of K₂Ta₄O₁₁. Thermal and X-ray diffraction analysis showed that the synthesis is completed at 900°C. Sintering studies showed that KTaO₃ powder can produce single phase ceramics with 85% of relative density with the addition of 5% of potassium excess when sintered at 1330°C for 1 h. Longer sintering times or higher temperatures result in enhanced potassium loss and consequent formation of K₆Ta_10.8O₃₀ secondary phase with tetragonal tungsten bronze structure. Room- and low-temperature microwave dielectric properties of KTaO₃ ceramics compare well with measurements performed on single crystals. We evaluated the influence of microstructural features (porosity, structural defects, secondary phases) on the dielectric properties of the ceramic samples.     

Effect of CuO on the Sintering Temperature and Piezoelectric Properties of (Na0.5K0.5)NbO3 Lead-Free Piezoelectric Ceramics

When a small amount of CuO was added to (Na_0.5K_0.5)NbO₃ (NKN) ceramics sintered at 960°C for 2 h, a dense microstructure with increased grains was developed, probably due to liquid-phase sintering. The Curie temperature slightly increased when CuO exceeded 1.5 mol%. The Cu²⁺ ion was considered to have replaced the Nb⁵⁺ ion and acted as a hardener, which increased the E _c and Q _m values of the NKN ceramics. High piezoelectric properties of k _p=0.37, Q _m=844, and ɛ₃ ^T /ɛ₀=229 were obtained from the specimen containing 1.5 mol% of CuO sintered at 960°C for 2 h.     

复合烧结助剂对Ca_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)TiO_3微波介质陶瓷低温烧结与性能研究

研究了以Ca_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)TiO_3(CLST-0.7)为基料,复合添加10 wt%CaO-B_2O_3-SiO_2(CBS)、4 wt%Li_2O-B_2O_3-SiO_2-CaO-Al_2O_3(LBSCA)和0～2 wt%CuO氧化物为烧结助剂的微波介质陶瓷的低温烧结行为及微波介电特性.结果表明:随着CuO添加量的增加,陶瓷体积密度、介电常数ε_r、无载品质因数与谐振频率乘积Qf值,都呈先增加后降低,频率温度系数τ_f呈降低的趋势.添加10 wt%CBS、4.0 wt% LBSCA和1.0 wt%CuO的CLST-0.7微波介质陶瓷,在900 ℃烧结5 h具有较佳的微波介电性能:ε_r ＝ 67.31,Qf ＝ 2197 GHz,τ_f＝40.28 ppm/℃.     

烧结助剂含量对多孔Si3N4/BN复合陶瓷力学性能和介电性能的影响

以Si3N4和BN为原料,叔丁醇为溶剂,SiO2、Y2O3和Al2O3为烧结助剂,采用凝胶注模成型工艺制备具有高强度、低介电常数多孔Si3N4/BN复合陶瓷。研究了Y2O3和Al2O3含量对多孔陶瓷气孔率、孔径分布、物相组成、显微结构、抗弯强度和介电常数的影响。结果表明:通过调节Y2O3和Al2O3含量,多孔Si3N4/BN复合陶瓷的气孔率由55%增加到68%,气孔尺寸呈单峰分布,平均孔径为0.89～1.02μm;抗弯强度和相对介电常数随Y2O3和Al2O3含量的增加而单调增大,抗弯强度和相对介电常数的变化范围分别为29.9～60.9 MPa和2.30～2.85;通过调节Y2O3和Al2O3含量调控气孔率,能够获得介电性能和力学性能可调的高性能透波材料。     

Dielectric and impedance spectroscopy of Bi(Ca0.5Ti0.5)O3 ceramic

Bismuth calcium titanate (BiCa_0.5Ti_0.5O₃) ceramic, fabricated by a ceramic processing technique, has been characterized using a variety of experimental techniques. Analysis of basic crystal structure using X-ray diffraction data exhibits the orthorhombic system. Measurements and detailed analysis of some electrical parameters (i.e.,dielectric constant, loss tangent (energy loss), electrical impedance and modulus, conductivity, etc.) of Bi(Ca_0.5Ti_0.5)O₃ in a wide range of frequency (10³–10⁶ Hz) and temperature (30–500 °C) have provided some interesting and useful data and results on structure–properties relationship, conduction mechanism, etc.The role of interface, space charge polarization and Maxwell–Wagner dielectric relaxation in getting high dielectric constant of the material at low frequencies and high temperatures has been discussed. Study of temperature dependence of Nyquist plots clearly shows the contributions of grains in resistive and capacitive properties of the material. The frequency of the applied electric field and temperature strongly affect the dielectric (permittivity and dissipation of energy) and electrical (impedance, electrical modulus and conductivity) characteristics of the material.     

B2O3-CuO掺杂CSLST微波介质陶瓷介电性能研究

选用B2O3-CuO(BC)低熔点复合氧化物作为烧结助剂,采用固相法制备(Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3(CSLST)陶瓷,研究了不同含量的BC对CSLST陶瓷的晶相组成、烧结性能及微波介电性能的影响.研究结果表明:随BC添加量的增多,CSLST陶瓷的烧结温度降低,陶瓷的微波介电常数εr和谐振频率温度系数(Τ)f下降,品质因素Qf明显降低.当BC添加量为5wt％时,在1000℃保温5h可烧结,此时陶瓷具有较佳的微波介电性能:εr=80.4,Q×f=1380 GHz,(Τ)f=- 32.89×10-6/℃.     

Synthesis and Microwave Dielectric Properties of MgSiO3 Ceramics

MgSiO₃ ceramics were synthesized and their microwave dielectric properties were investigated. The Mg₂SiO₄ phase was formed at temperatures lower than 1200°C, while the orthorhombic MgSiO₃ phase started to form by the reaction of SiO₂ and Mg₂SiO₄ in the specimen fired at 1200°C. The structure of the MgSiO₃ ceramics was transformed from orthorhombic to monoclinic when the sintering temperature exceeded 1400°C. A dense microstructure was developed for the specimens sintered at above 1350°C. The excellent microwave dielectric properties of ɛ_r=6.7, Q × f =121 200 GHz, and τ_f=−17 ppm/°C were obtained from the MgSiO₃ ceramics sintered at 1380°C for 13 h.     

Low-Temperature Sintering and Microwave Dielectric Properties of Li2MgSiO4 Ceramics

Development of a low-temperature sintered dielectric material derived from Li₂MgSiO₄ (LMS) for low-temperature cofired ceramic (LTCC) application is discussed in this paper. The LMS ceramics were prepared by the solid-state ceramic route. The calcination and sintering temperatures of LMS were optimized at 850°C/4 h and 1250°C/2 h, respectively, for the best density and dielectric properties. The crystal structure and microstructure of the ceramic were studied by the X-ray diffraction and scanning electron microscopic methods. The microwave dielectric properties of the ceramic were measured by the cavity perturbation method. The LMS sintered at 1250°C/2 h had ɛ_r=5.1 and tan δ=5.2 × 10⁻⁴ at 8 GHz. The sintering temperature of LMS is lowered from 1250°C/2 h to 850°C/2 h by the addition of both lithium borosilicate (LBS) and lithium magnesium zinc borosilicate (LMZBS) glasses. LMS mixed with 1 wt% LBS sintered at 925°C/2 h had ɛ_r=5.5 and tan δ=7 × 10⁻⁵ at 8 GHz. Two weight percent LMZBS mixed with LMS sintered at 875°C/2 h had ɛ_r=5.9 and tan δ=6.7 × 10⁻⁵ at 8 GHz.