添加TiO2对Mg4Nb2O9陶瓷的结构与性能的影响

Mg4Nb2O9具有与α-Al2O3相同的刚玉型晶体结构,可望成为新一代高Q、低ε基板材料.然而,该材料却具有很大的负谐振频率温度系数(τf=-7.05×10-5/℃),期望通过添加TiO2(τf=4.50×10-4/℃)以达到调整的目的.适量的添加TiO2将Mg4Nb2O9陶瓷的烧结温度降低了约100℃,并增强了陶瓷的性能,微波介电性能与其密度呈线性关系.由于添加的TiO2与Mg5Nb4O15反应形成了(Ng,Ti)5(Nb,Ti)4O15第二相,使得TiO2对该陶瓷τf值的调整作用不显著.1300℃、5h烧结添加质量分数为2.5%的TiO2的Mg4Nb2O9陶瓷具有最佳的性能:εr=13.61,Q·f=196620GHz,τf=-5.04×10-5/℃.     

Spinel Mg(Al,Ga)2O4 Solid Solution as High‐Performance Microwave Dielectric Ceramics

Spinel Mg(Al_1?xGa_x)₂O₄ (x = 0–1) solid solutions were synthesized via solid‐state method. Replacement of Al³⁺ by Ga³⁺ in MgAl₂O₄ gave rise to the expansion of the lattice, as well as blueshifts of FT‐IR and Raman peaks. The homogeneous solid solutions, high relative densities, large grain sizes, and compact microstructures resulted in excellent microwave dielectric properties for spinel Mg(Al_1?xGa_x)₂O₄ (x = 0.6) ceramics sintered at 1485°C: that is, ε_r = 8.87, Q × f = 107 000 GHz (at 14.8 GHz), and τ_f = ?16 ppm/°C. Spinel‐structured Mg(Al_1?xGa_x)₂O₄ (x = 0–1) solid solutions possessed low sintering temperatures, wide temperature regions (~100°C), and small negative τ_f values. These outstanding performance make Mg(Al, Ga)₂O₄ a promising candidate material for millimeter‐wave devices.     

MgO/MgF2掺杂对Al2O3陶瓷烧结、显微结构及微波介电性能的影响

采用搅拌混合法和无压烧结工艺,制备了Mg2+浓度为500 ppm的MgO掺杂和MgF2掺杂的Al2O3陶瓷,系统地研究了MgO和MgF2掺杂对Al2O3陶瓷致密化、显微结构和微波介电性能的影响.研究结果表明:与MgO掺杂相比,MgF2掺杂在较高温度下能更加有效地促进Al2O3陶瓷的致密化.在1550℃烧结条件下,MgF2掺杂的Al2O3陶瓷比MgO掺杂的Al2O3陶瓷的晶粒更大,同时介电常数也更高.但另一方面,MgF2掺杂的Al2O3陶瓷介电损耗也远比MgO掺杂的Al2O3陶瓷要高.同时简单分析了造成此现象的原因.     

Mg4(Mb2-xSbx)O9陶瓷的制备与微波介电性能

采用传统固相反应法制备了Mg4(Nb2-xSbx)O9陶瓷,研究了该材料的烧结性能、物相结构、显微组织和微波介电性能.X射线衍射结果显示,在x小于或等于1.6的范围内,形成了具有α-Al2O3刚玉型晶体结构的连续固溶体,晶轴长度和晶胞体积均随着锑含量的增加而降低.在x等于2.0时,Mg4Sb2O9的物相结构发生了变化,晶轴长度和晶胞体积也发生了突变.当0.4≤x≤O.8时,陶瓷的烧结温度从1400℃降低到了1300℃;而当x≥1.2后,陶瓷的烧结性能和微波介电性能均降低.在1300℃,5h的烧结条件下,Mg4(Nb1.6Sb0.4)O9陶瓷的微波介电常数(εr)为12.26,Q·f为168450 GHz.     

Ca0.7Ti0.7La0.3Al0.3O3微波介质陶瓷微观组织结构与介电性能

采用固相反应法制备斜方晶系钙钛矿结构Ca07Ti07La0.3Al0.3O3微波介质陶瓷,研究了Al3+、Ca2、Ba2+和La3+离子掺杂对CTLA陶瓷微观组织结构和介电性能的影响.研究结果表明不同掺杂离子对于CTLA陶瓷的微观结构和介电性能有很大的影响,不同离子掺杂CTLA陶瓷的晶粒尺寸、气孔率、晶界析出相有很大的不同.Al3+、Ca2+、Ba2+和La3+离子掺杂可以有效降低CTLA陶瓷的谐振频率温度系数,但Ca2+、Ba2+离子掺杂同时也降低了CTLA陶瓷的致密度和Q×f值,Al3+、La3+离子掺杂不仅有效提高了CTLA陶瓷的致密度和Q×f值,并且有效降低了谐振频率温度系数.适量掺杂La3离子可以有效促进CTLA陶瓷的致密化,提高了CTLA陶瓷的微波介电性能.掺杂0.15mol％ La3+的CTLA陶瓷在4.7 GHz下测试介电性能为:εr=48.39,Q×f=32560 GHz,τf=23.68 ppm/C.     

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.     

Synthesis and Microwave Dielectric Properties of Cu‐Doped ZnAl2O4

Spinel materials of composition Zn_1?xCu_xAl₂O₄ (ZCA, x = 0–0.015) were prepared via the conventional solid‐state route. The lattice structure, microstructure, and microwave dielectric properties were investigated as a function of Cu content. Cu doping was found to improve the sinterability and, meanwhile, significantly increase the quality factor (Q × f₀), which is due to the Cu‐O bond is stronger than Zn‐O bond, and inhibit the oxygen vacancy considered to be responsible for the enhanced Q × f₀ value of ZCA materials. The best microwave dielectric properties were obtained in Zn_0.99Cu_0.01Al₂O₄ with ε_r = 8.69, Q × f₀ = 69,300 GHz and τ_f = ?58.3 ppm/°C, which was sintered at 1520°C for 3 h in air.     

低温烧结Mg4Nb2O9微波介质陶瓷

研究了V2O5对Mg4Nb2O9陶瓷的烧结温度、相结构和微波介电性能的影响.结果表明,添加1％～8％的V2O5,能使该陶瓷的烧结温度降低到1000～1050℃而对其微波介电性能的影响很小,材料的主晶相为有序型刚玉结构的Mg4 Nb2O9,存在Mg4Nb2O6和Mg5Nb4O15杂相而没有检测到V2O5的存在.陶瓷的密度对微波介电性能起着决定性作用,介电常数e1与密度成线性关系(在99.99％的置信限内,其相关系数为0.98252),Q·f值与密度的关系较复杂.添加1％的v2O5,将Mg4Nb2O9陶瓷的烧结温度降低到了1050℃,得到了εr=12.72,Q·f=151040GHz的优异性能.     

高能球磨时间对MgNb2O6陶瓷显微结构和微波介电性能的影响

采用高能球磨法制备粉体,研究了粉体球磨时间对MgNb2O6陶瓷显微结构和微波介电性能的影响,结果表明,1180℃烧结陶瓷,随球磨时间增加,平均粒径减小,气孔率降低,相对密度增大,介电常数增大;升高烧结温度到1220℃以上,不同球磨时间制备陶瓷样品相对密度达到95.8％以上,平均晶粒尺寸3.5m,εr为19.7,而Qxf值随球磨时间先增大后减小.高能球磨制备粉体能有效促进MgNb2O6陶瓷在1220℃下中温烧结,且具有优良的微波介电性能(εr=19.7,Q×f=28 744 GHz),有望成为新一代中温烧结高频微波介质基板材料.     

Low‐Temperature Synthesis of CoNb2O6 Microwave Dielectric Ceramics

Low‐fired cobalt niobate (CoNb₂O₆) microwave dielectric ceramics were prepared through a developed sol–gel process using Nb₂O₅·nH₂O as starting source. A metal‐dioxo‐bridged complex precursor was described on the basis of FT‐IR spectrum. The crystalline phases of calcined powders were characterized by X‐ray diffraction. Nanosized CoNb₂O₆ particles with orthorhombic α‐PbO₂‐type structure were obtained above 750°C. There was no subsequent phase change upon sintering, and all compounds sintered to at least 94% of theoretical density. At 1000°C/4 h, CoNb₂O₆ ceramics exhibited ε_r ~ 21.9, Q × f ~ 66 140 GHz (at 8.9 GHz) and τ_f ~ ?39.7 ppm/°C, having a good potential for low‐temperature cofired ceramic applications.     

富含CuO的CaCu_3Ti_4O_(12)陶瓷显微结构和介电性能的研究

CaCu3Ti4O12陶瓷具有巨介电性,有助于电容器、存储器等电子器件向高性能化和尺寸微型化的进一步发展。研究了富含CuO对CaCu3Ti4O12陶瓷的显微结构和介电性能的影响,结果表明:富含CuO可促进CaCu3Ti4O12陶瓷晶粒的长大和提高均匀性,富含CuO有利于增加CaCu3Ti4O12陶瓷的介电性能的稳定性,且介电性能的稳定性跟陶瓷晶粒的均匀性有着一定的关系。     

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/℃.     

Impedance Spectroscopy,Broadband, and Microwave Dielectric Properties of Mechanically Alloyed Ba5Nb4O15 Ceramics

Ba₅Nb₄O₁₅ (BNO) ceramics were synthesized by the mechanical alloying method. The transmission electron microscope images of BNO powders revealed rod‐shaped grains. Mechanically alloyed BNO exhibited maximum density of 97.3% and is explained on the basis of Herring's scaling law. Both the dielectric constant and loss tangent show a stable response up to 0.2 GHz. Further, the dielectric response of BNO ceramics measured above 350°C shows relaxation behavior and is explained using Havriliak–Negami equation. The obtained stable dielectric response of BNO is suitable for type I capacitor and dielectric resonator applications.     

Nd2O3掺杂对BCZT陶瓷结构及介电性能的影响

采用固相反应法制备Ba0.92-xCa0.08Ndx(Zr0.18Ti0.815Y0.0025Mn0.0025)O3(BCZT-Nd,x=0、0.005、0.010、0.020)陶瓷,研究了Nd2O3掺杂对Ba0.92Ca0.08(Zr0.18Ti0.82)O3(BCZT)陶瓷结构及介电性能的影响。结果表明,不同含量Nd3+作为施主掺杂离子进入A位和含量均为0.25%(摩尔分数)的Mn2+和Y3+作为受主掺杂进入B位均能提高BCZT陶瓷的致密性,细化晶粒作用明显,所有样品均为单一的四方BaTiO3相结构。随Nd2O3掺杂量增加,BCZT-Nd陶瓷介电峰值温度Tm向低温方向移动,相变弥散程度增强,Nd3+含量≥0.005mol时即表现出明显的弛豫铁电体特征。     

TiO_2含量对微波介质瓷Zr_xTi_(1-x)O_2致密化、微结构及介电性能的影响

制备了一系列ZrxTi1-xO2(x =0.40~0.60)微波介质瓷,对其致密化、微结构及介电性能进行了研究. XRD物相分析样品为单一均相的ZrTiO4. 在相同的烧结温度下,TiO2含量越高,样品越不易致密,相对密度越低,晶粒越易长大. 样品的相对密度越高,其介电常数和品质因数越大. 相对密度高于90%时,对样品介电性能的影响可以忽略,成份起主导作用. 随着TiO2含量增加,样品的介电常数增大,品质因数降低.     

Effect of Glass Addition on the Microwave Dielectric Properties of CaMgSi2O6 Ceramics

CaMgSi₂O₆ (CMS) ceramics prepared by the solid-state ceramic route have a sintering temperature of 1300°C/2 h. The sintering temperature of CMS was reduced below the melting point of Ag using low-melting LBS and LMZBS glasses. In the case of CMS+15 wt% LMZBS sintered at 900°C/2 h, the dielectric properties obtained were ɛ_r=8.2, Q_u×f=32,000 GHz (10.15 GHz), and τ_f=–48 ppm/°C. The CMS+15 wt% LBS composite, sintered at 925°C/2 h, showed ɛ_r=8, Q_u×f=15,000 GHz (10.17 GHz), and τ_f=–49 ppm/°C. The chemical compatibility of Ag with the ceramic–glass composites was also investigated for low-temperature co-fired ceramic applications.     

Structure and Microwave Dielectric Properties of Low Firing Bi2Te2W3O16 Ceramics

Dense Bi₂Te₂W₃O₁₆ ceramics were prepared by the conventional solid‐state reaction route. X‐ray diffraction data show the room‐temperature (RT) crystal symmetry of Bi₂Te₂W₃O₁₆ to be well described by the centrosymmetric monoclinic C2/c space group [a = 21.280(5) Å, b = 5.5663(16) Å, c = 12.831(3) Å and β = 124.014(19)° and Z = 4]. Raman spectroscopy analyses are in broad agreement with space group assignment, but also revealed the presence of Bi₂W₂O₉ as a secondary phase. This phase is present as plate‐like grains embedded on a fine‐grained equiaxed matrix, as revealed by scanning electron microscopy. From the fitting of infrared reflectivity data the relative permittivity, ε_r, was estimated as 34.2, and the intrinsic quality factor, Q_u × f as 57 500 GHz. At RT and microwave frequencies, Bi₂Te₂W₃O₁₆ ceramics sintered at 720°C for 6 h exhibit ε_r ~ 34.5, Q_u × f = 3173 GHz (at 7.5 GHz), and temperature coefficient of resonant frequency, τ_f = ?92 ppm/°C. This shows a good agreement between the estimated and measured ε_r values, but also shows that, in principle, the dielectric losses of the ceramics are of extrinsic origin.     

低介电常数(Mg_(1–x)Y_x)_2Al_4Si_5O_(18)陶瓷的制备与微波介电性能

采用传统陶瓷固相反应烧结法制备(Mg1–xYx)2Al4Si5O18陶瓷。Y3+掺杂产生液相烧结作用,使得堇青石陶瓷的烧结温度从1 450℃降低到1 325℃。结果表明:(Mg1–xYx)2Al4Si5O18陶瓷在0≤x0.05范围内,以(Mg,Y)2Al4Si5O18固溶体形式存在;在0.05≤x0.25范围内,以Mg2Al4Si5O18/Y2Si2O7复相陶瓷形式存在。Y3+能够改善(Mg1–xYx)2Al4Si5O18陶瓷的颗粒尺寸分布,并使陶瓷的气孔率降低。(Mg1–xYx)2Al4Si5O18陶瓷的相对介电常数由x=0的6.15提高到x=0.05的6.31;然后逐渐降低至x=0.25的5.90。品质因数Qf值由x=0的33 000 GHz提高到x=0.05的41 000 GHz,然后降低至x=0.25的24 000 GHz。谐振频率温度系数(0.05≤x0.25)值从–32×10–6/℃提高到–24×10–6/℃。     

Microwave Dielectric Properties of Ultralow‐Temperature Cofirable Ba3V4O13 Ceramics

Ultralow‐temperature sinterable Ba₃V₄O₁₃ ceramics have been prepared through solid‐state ceramic route. Structural properties of the ceramic material are studied using powder X‐ray diffraction. Ba₃V₄O₁₃ ceramic has monoclinic structure and the existence of [V₄O₁₃]^6? polyhedra is confirmed through Laser Raman studies. The sample sintered at 600°C for 1 h shows dense microstructure with microwave dielectric properties of ε_r = 9.6, Q × f = 56 100 GHz, and τ_f = ?42 ppm/°C. The ceramics under study show good chemical compatibility with aluminum during cofiring.     

BaO-Nd2O3-Sm2O3-TiO2四元系微波介质陶瓷

本文研究了Bi2O3、PbO及Sm2O3对BaO-Nd2O3-TiO2(简称BNT)系陶瓷材料微波性能的影响.实验表明,在BNT系材料中掺入Bi2O3或PbO可降低材料的频率温度系数τf,但同时也使材料的tgδ增大.采用Sm取代部分Nd,形成BaO-Nd2O3-Sm2O3-TiO2(简称BNST)四元系陶瓷材料,可有效降低材料的τf,改善频率温度稳定性,而不会降低材料的品质因素Q0.当Sm2O3∶Nd2O3=7∶3(mol比)时,可得到εr=80.80,tgδ=2.92×10-4(2.7GHz测),τf=23.63ppm/℃的高性能BNST四元系微波介质陶瓷材料.