Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Sm_(0.5)TiO_3复合微波陶瓷的介电性能

采用传统固相合成法制备了xCa0.6La0.8/3TiO3-(1-x)(Li0.5Sm0.5)TiO3(CLT-LST)系列微波介质陶瓷材料,研究了该系列微波介质陶瓷的物相结构、表面形貌、介电性能。实验发现:随着Ca0.6La0.8/3TiO3含量的增多,CLT-LST样品XRD峰轻微左移。陶瓷组成对微波介电性能影响显著,复合体系CLT-LST的微波介电性能随着x值不同而连续变化:当x从0.2上升到0.6时,介电常数(εr)逐步增大,在x=(0.4~0.6),εr变化趋于稳定,达到较佳值;品质因数(Q·f)则先减小后增大再迅速减小;谐振频率温度系数(τf)逐渐从负值向正值方向移动。当复合体系组成为0.4Ca0.6La0.8/3TiO3-0.6(Li0.5Sm0.5)TiO3时,在1 250℃烧结4h所得到的微波介电性能较佳,εr=125;Q·f=2 680GHz;τf=7.0×106/℃。     

前驱体制备(1-x)CaTiO3-xCa(Zn1/3Nb2/3)O3陶瓷的微波介电性能

以ZnNb2O6为前驱体,通过固相反应合成了(1-x)CaTiO_3-xCa(Zn_(1/3)Nb_(2/3))O_3体系微波介质陶瓷。对固溶体进行了结构与性能测试,研究了体系结构与性能随组份变化规律。结果表明,由于Zn,Nb对Ti的B位取代增大了B-O八面体的倾斜角,从而导致随着Ca(Zn_(1/3)Nb_(2/3))O_3含量从0.2增加至0.8,介电常数从109减小为49,Q×f值从8340GHz增至13200GHz,频率温度稳定系数由321ppm/℃降为-18ppm/℃。在x=0.7时获得ε_1≈56,Q×f≈11500GHz,τ_f≈-5ppm/℃的最佳性能。     

(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3复合体系的微波介电性能

采用固相合成法制备了(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3系列微波介质陶瓷材料.研究了复合系统的微波介电性能和微观结构.研究结果表明在y=0.4～0.6范围内,体系形成了单一的钙钛矿结构.当复合体系组成为0.5Ca0.6La0.267TiO3-0.5Ca(Mg1/3·Nb2/3)O3时,在1 400℃下烧结保温4 h所制备的材料表现出良好的微波介电性能εr=55,Q×f=45 000 GHz(7.6 GHz下),τf=0.04×10-6/℃.     

(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3复合微波介质陶瓷的研究

采用固相合成法制备了 ( 1-y)Ca1 -xLa2x/ 3 TiO3 -yCa(Mg1 / 3 Nb2 / 3 )O3 系列微波介质陶瓷材料 ,研究了复合系统的微波介电性能、烧结性能和微观结构。研究结果表明 :在y =0 .4～ 0 .6范围内 ,体系形成了单一的钙钛矿结构 ;当复合体系组成 0 .5Ca0 .6La0 .2 67TiO3 -0 .5Ca(Mg1 / 3 Nb2 / 3 )O3 时 ,在 14 0 0℃下烧结保温 4小时所得到材料的微波介电性能最佳 ;εf=5 5 ,Q×f =45 0 0 0GHz( 7.6GHz下 ) ,τf=0 .0 4ppm/℃。     

BaCu(B_2O_5)掺杂对0.4CaTiO_3-0.6(Li_(1/2)Nd_(1/2))TiO_3陶瓷烧结和介电性能的影响

研究了烧结助剂BaCu(B2O5)(BCB)对0.4CaTiO3-0.6(Li1/2Nd1/2)TiO3(CLNT)介质陶瓷的烧结特性、相组成、微观形貌及介电性能的影响。结果表明:添加少量的BCB能使CLNT陶瓷的烧结温度从1300℃降低至1050℃。随着BCB添加量的增加,介电常数下降,频率温度系数向负值偏移。添加4wt%BCB的CLNT陶瓷在1050℃烧结2h,获得了最佳的介电性能:εr=96.5,tanδ=0.017,τf=-13.6ppm/℃,满足高介多层片式微波元器件的设计要求。     

MgSn0.05Ti0.95O3-SrTiO3复相陶瓷的显微结构与微波介电性能

采用传统固相法制备了不同摩尔配比的(1-x)MgSn0.05Ti0.95O3-xSrTiO3微波介质复相陶瓷材料,研究了复相陶瓷的烧结特性、显微结构和微波介电性能.结果表明:MgSn0.05Ti0.95O3和SrTiO3两相共存,无固溶现象.随着SrTiO3含量的增多,(1-x) MgSn0.05Ti0.95O3-xSrTiO3的相对介电常数(εr)线性增大,品质因数(Q×f)下降,谐振频率温度系数(τf)从负值变为正值.通过调节x值,可以获得近零的τf值.陶瓷的τf变化符合Lichtenecker混合法则.0.98MgSn0.05Ti0.95O3-0.02SrTiO3复相陶瓷在1330℃烧结4h,获得最佳的微波介电性能:εr=19.32,Q×f=193.527 THz,τf=-2×10-6/℃.     

(Ba1-xSrx)(Mg1/3 Ta2/3)O3微波陶瓷介电性能研究

Ba(Mg1/3Ta2/3)O3(简称BMT)陶瓷是A(B′1/3B″2/3)O3(A=Ba,Sr;B′=Zn,Mg;B″=Nb,Ta)型复合钙钛矿化合物中的一种,A位由Sr离子取代Ba离子,形成(Ba1-xSrx)(Mg1/3Ta2/3)O3(简称BSMT)固溶体型化合物,也具有复合钙钛矿结构。Sr含量x≥0．6时发生相转变,形成一种新的低温相,这是由于氧八面体畸变造成的。这种低温相结构与BMT六方晶系结构相比具有较低的对称性。低温相的形成．可显著降低BSMT陶瓷的烧结温度．在150℃即可烧结致密(BMT为160℃)。BSMT的微观结构和介电性能(如介电常数ε和介电常数温度系数aε)的变化也与此相转变有关。     

Li2Zn3(1-x)Ca3xTi4O12微波陶瓷介电性能研究

本文以Li2CO3,ZnO,CaCO3,TiO2为原料,采用固相反应法制备了Li2Zn3(1-x)Ca3xTi4O12(x=0,0.05,0.1,0.15)陶瓷,并研究了CaTiO3固溶量对其显微结构和微波介电性能的影响.结果表明:Li2Zn3Ti4O12晶相中固溶CaTiO3相,晶胞参数会增大;少量CaTiO3相固溶于Li2Zn3Ti4O12陶瓷后,提高了Li2Zn3Ti4012陶瓷的烧结温度及其介电常数,但降低了其品质因素,可增大其温频系数.在1100℃/2 h烧结条件下,Li2Zn2.7Ca0.3Ti4O12陶瓷微波介电性能达到:εr=24,Q×f=50000 GHz,Tf=-25×10-6/℃.     

复合钙钛矿陶瓷的结构与微波介电性能

介绍了复合钙钛矿化合物结构的本质特征，讨论了钙钛矿结构对微波介质陶瓷材料的介电性能（介电常数、介质损耗、频率温度系数）的各种影响因素。     

Pr2O3取代Sm2O3对CLST微波介质陶瓷介电性能的影响

论述了使用Pr2O3取代Sm2O3对CaO-Li2O-Sm2O2—TiO2（CLST）微波介质陶瓷介电性能的影响。采用传统固相反应法制备16CaO-9Li2O-xPr2O3-（12-x）Sm2O3-63TiO2（简写为CLPST-x）陶瓷。XRD分析结果表明，不同取代量的CLPST-x呈现单一的正交钙钛矿结构。当CaO：Li2O：Pr2O3：Sm2O3：TiO2=16：9：4：8：63，烧结温度为1300℃时．CLPST-x能够取得良好的介电性能。εr=101，tanδ=0．00923，τr=85ppm／℃（1MHz），此时，晶粒大小均匀，晶界清晰。     

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.     

Structure and microwave dielectric properties of 1:1 ordered Nd[(Mg1-xZnx)1/2Ti1/2]O3 complex perovskite ceramics

Nd[(Mg_1-xZn_x)_1/2Ti_1/2]O₃ perovskite ceramics (x = 0, 0.2, 0.4, 0.6, 0.8) are prepared by the solid-state reaction method. The effects of Zn²⁺ substitution on the structure, microstructure, especially the B-site 1:1 cation ordering and microwave dielectric properties have been investigated. Sintered Nd[(Mg_1-xZn_x)_1/2Ti_1/2]O₃ ceramics all adopt dense microstructure, along with increased dimensional uniformity as Zn²⁺ substitution. All the ceramics are confirmed to have B-site 1:1 ordered monoclinic perovskite structure with P2₁/n space group. Atomic mass difference of B-site elements might be an important factor affecting the B-site 1:1 cation ordering. HRSTEM observation suggest that the doped Zn²⁺ cations have roughly entered the Mg²⁺ sites to promote 1:1 cation ordering. The degree of the 1:1 cation ordering can be negatively reflected by the full width at half maximum (FWHM) of F_2g(B) mode at 372 cm^?1 in Raman spectra. With Zn²⁺ doping, the degree of the 1:1 cation ordering first increases then decreases, and reaches its maximum at x = 0.6. Meanwhile the best combination of microwave dielectric properties is obtained, as ε_r = 31.4, Q × f = 74,000 GHz, τ_f = ?44 ppm/°C. It is found that the long-range ordering not only decreases the dielectric loss but also affects the dielectric constant, providing a theoretical foundation to understand further the correlation between ionic configuration and microwave dielectric properties.     

The Role of Microstructure on Microwave Dielectric Properties of (Ba,Sr)TiO3 Ceramics

Microstructural effects on the microwave dielectric properties of (Ba_0.4Sr_0.6)TiO₃ (BST) polycrystalline ceramics were investigated, focusing on the grain size. Sintering temperatures between 1350°C and 1500°C have a strong effect on the permittivity (880 < ε_r < 990), quality factor (570 GHz < Q×f < 1150 GHz), and temperature coefficient of resonant frequency (3920 ppm/°C < τ_f < 4560 ppm/°C) at microwave frequency (≈1.4 GHz). The tunable permittivity characteristics (measured at 10 kHz), were also found to be sensitive to the sintering process, demonstrating the possibility of tailoring material property by designed processing. In addition, the effect of the sintering process on grain structure was investigated by XRD calculation and Raman scattering characterization. Less confined phonons were believed to contribute to the enhanced microwave performance as an intrinsic effect (grain size effect), for samples with higher sintering temperature and longer dwell time. On the contrary, the macroscopic properties tend to saturate (or deteriorate), for samples at intensified sintering condition, being thought to be dominated by the extrinsic factors (such as the abundant defects in large grains), as confirmed by the SEM observations.     

Improvement of microwave dielectric properties for Ba(Ni1/3Nb2/3)O3 ceramics by Zr-substitution

Effects of Zr-substitution on the structure, microstructure and microwave dielectric properties of Ba(Ni_1/3Nb_2/3)O₃ ceramics have been investigated. A small amount of Zr-substitution facilitates the densification of Ba(Ni_1/3Nb_2/3)O₃ ceramics. Within x≤0.05, the densification temperature decreases with increasing x in Ba[(Ni_1/3Nb_2/3)_1−xZr_x]O₃, while it turns to increase for x>0.05. With increasing x, the grains become more homogeneous and closely contacted, and significantly increase in size for x=0.15–0.20. The B-site cations 1:2 ordering is destroyed by Zr-substitution, and only stabilizes for x≤0.04. B-site cations 1:1 ordering starts to form in x=0.04, and the 1:1 ordering degree first increases and then decreases with increasing x. Qf value decreases slightly in x=0.01 and then increases monotonously with x increasing from 0.02 to 0.20. The destroyed 1:2 ordering structure is responsible for the decreased Qf value in x=0.01, while the improved grain configuration dominates the increase of Qf value for x=0.02–0.20. The dielectric constant ε_r increases monotonously with increasing x, due to the higher polarizability of Zr ion than the average value of Ni/Nb ions. The temperature coefficient of resonant frequency τ_f shifts from negative to positive through zero with increasing x, which is ascribed to the highly positive τ_f value of the end member BaZrO₃. The significant improvement of microwave dielectric properties has been achieved for x=0.10, higher ε_r, higher Qf as well as near zero τ_f value have been obtained: ε_r=31.8, Qf=36,100 GHz, τ_f=7.8 ppm/°C.     

低温烧结微波介质陶瓷（1－x）Ba3（VO4）2-xLi2 MoO4的微波性能研究

采用固相反应制备了（1－x）Ba3（VO4）2-xLi2MoO4微波介质陶瓷,研究了掺入不同质量比的Li2MoO4对Ba3（VO4）2的微观结构和微波介质性能影响,X线衍射（XRD）测试结果表明,Ba3（VO4）2和Li2MoO4二者兼容性良好,无第二相产生。添加具有低熔点及相反（负）频率温度系数的Li2 MoO4能有效降低Ba3（ VO4）2的烧结温度,并随着添加剂Li2 MoO4的增加,此复合陶瓷的相对体密度、介电常数εr 和品质因数Q ×f呈现出先增加随后又降低的趋势,而谐振频率里面温度系数τf逐渐降低。当烧结温度为660℃且添加量30wt％Li2 MoO4的复合微波介质陶瓷获得了最佳的微波介电性能：εr ＝11．99, Q ×f＝39700 GHz,τf ＝－24 ppm／℃。     

(1-x)(Bi1/2Na1/2)0.900Ba0.088Sr0.012TiO3-x(Bi1/2K1/2)TiO3无铅压电陶瓷的电学和力学性能

利用常规烧结方法制备出了多种A位离子掺杂的钛酸铋纳[(Bi1/2Na1/2)TiO3,BNT]无铅压电陶瓷.对BNT基陶瓷的电学性能和力学性能进行了研究.在(1-x)(Bi1/2Na1/2)0.900Ba0.088Sr0.012TiO3-x(Bi1/2K1/2)TiO3(x=0-0.14)陶瓷体系中,当x=0.10时,可获得最大压电常数(168pC/N).在1 kHz,这种陶瓷的介电常数、介电损耗和平面机电耦合系数分别为1 221,0.0361和0.2281.Curie温度随x的增加先增加,当x=0.12时,达到最高值(300℃),随后,当x值进一步增加,Curie温度降低.该种无铅压电陶瓷的Vickers硬度和断裂韧性分别为5.0GPa和2.0MP·m1/2,均高于Pb(Zr,Ti)O3陶瓷.     

Structure and dielectric properties of novel low temperature co-fired Bi2O3-RE2O3-MoO3 (RE=Pr,Nd, Sm,and Yb) based microwave ceramics

Novel monoclinic Bi₂O₃-xRE₂O₃-yMoO₃ (RE=Pr, Nd, Sm, and Yb) based low temperature co-fired ceramics (LTCC) systems with high sintering density and low microwave dielectric loss are synthesized by conventional solid state reaction technique. The structure and dielectric properties of Bi₂O₃-xRE₂O₃-yMoO₃ ceramics are investigated. Dense BiNdMoO₆ ceramics sintered at 900 °C for 8 h in air have a low dielectric constant ε_r=~7.5, a high quality factor Q×f=~ 24, 800 GHz at 7.0 GHz, and τ_f=~−16 ppm/̊C. Especially, good chemical compatibility of BiNdMoO₆ with Ag electrodes is represented as well. In contrast, BiSmMoO₆ ceramics sintered at 1000 °C for 8 h show enhanced Q×f=~43, 700 GHz at 7.8 GHz with ε_r=~8.5 and τ_f=~−27 ppm/°C. Bi₂O₃-xRE₂O₃-yMoO₃ (RE=Pr, Nd, Sm, and Yb) based ceramics could be considered as promising microwave ceramics for LTCC applications.     

CaTiSiO5掺杂对钛酸钡锶陶瓷介电性能的影响

采用传统固相烧结法,利用X-射线衍射仪(XRD)、扫描电镜(SEM)等方法系统研究了CaTiSiO5掺杂量对(Ba,Sr) TiO3(barium strontium titanate,BST)基电容器陶瓷介电性能和微观结构的影响.结果表明:CaTiSiO5掺杂的BST陶瓷材料的介电损耗都比较小,但是对材料居里峰的移动和展宽效应都明显.随着CaTiSiO5掺杂量的增加,BST陶瓷的介电常数(εr)先增大然后减小,介电损耗(tanδ)先增大然后减小,变化不大,交流耐压强度(Eb)先增大然后减小,容温变化率先减小然后增大.当掺杂CaTiSiO5质量分数为0.8％时,BST陶瓷的综合介电性能较好:介电常数(εr)=2540,介电损耗(tanδ)=0.0036,耐压强度(Eb)=5.6 kV/mm(AC),在-30～85℃温度范围内,容温变化率为-18.9％ ～ 20.6％,容温特性符合Y5S特性.