V_2O_5与Al_2O_3复合改性CaSiO_3陶瓷的烧结性能与微波介电性能

为降低CaSiO3陶瓷的烧结温度,通过在CaSiO3粉体中添加1wt%的Al2O3以及不同量的V2O5,探讨了V2O5添加量对CaSiO3陶瓷烧结性能、微观结构及微波介电性能的影响规律。结果表明:适量地添加V2O5除了能将V2O5-Al2O3/CaSiO3陶瓷的烧结温度从1 250℃降低至1 000℃外,还能抑制CaSiO3陶瓷晶粒异常长大并细化陶瓷晶粒。在烧结过程中,V2O5将熔化并以液相润湿作用促进CaSiO3陶瓷的致密化进程;同时,部分V2O5还会挥发,未挥发完全的V2O5将与基体材料反应生成第二相,第二相的出现将大幅降低陶瓷的品质因数。综合考虑陶瓷的烧结性能与微波介电性能,当V2O5添加量为6wt%时,V2O5-Al2O3/CaSiO3陶瓷在1 075℃下烧结2h后具有良好的综合性能,其介电常数为7.38,品质因数为21 218GHz。     

Fe2O3掺杂MgTiO3-CaTiO3微波陶瓷的介电性能研究

采用固相法制备0.93MgTiO3-0.07CaTiO3-xFe_2O_3(摩尔分数x=0.01~0.025)微波介质陶瓷材料,研究添加Fe_2O_3后,体系的晶体结构、显微结构和微波介电性能之间的变化规律。利用XRD、SEM、网络分析仪对样品的相组成、微观结构、介电性能进行测试分析。研究表明:该复合陶瓷样品的致密度、介电常数和Q·f值随Fe_2O_3含量的增加先增大后减小。当x(Fe_2O_3)为0.015,在1290℃烧结4h时,获得最优的介电性能:εr=21.32,Q·f=37448GHz,τf=0.577×10-6/℃。     

BaO-B2O3-SiO2玻璃助剂对ZST陶瓷烧结和性能的影响

研究了BaO-B2O3-SiO2玻璃助剂对TiO2/Zn2SiO4(ZST)复合陶瓷的烧结特性和微波介电性能的影响.BaO-B2O3-SiO2玻璃助剂在烧结过程中能形成液相,有效地将ZST复合陶瓷的烧结温度从1340℃降低至970℃.随助剂用量的增加,Zn2SiO4陶瓷的介电常数(εr)略有提高,品质因数与频率的乘积(Q×f)下降,频率温度系数(τf)无明显变化.添加8%(质量分数,下同)BaO-B2O3-SiO2玻璃助剂和一定质量比的TiO2(m(TiO2):m(Zn2SiO4)=11:89)的ZST复合陶瓷在970℃保温4h,具有较好的微波介电性能:εr=8.70,Q×f=21280GHz,τf=-9×10-6/℃.     

Bi2O3掺杂对Mg4Nb2O9陶瓷的微结构及微波介电性能的影响

采用固相反应法制备了Mg4Nb2O9基微波介质陶瓷,研究了Bi2O3掺杂对Mg4Nb2O9陶瓷烧结行为、相结构、显微结构及微波介电性能的影响。实验结果表明:Mg4Nb2O9陶瓷烧结温度随Bi2O3掺杂量的增加而减小,添加2.0wt%Bi2O3,烧结温度从1350℃降低至1175℃;随Bi2O3添加量从0.0wt%增大到3.0wt%,最强峰(104)晶面间距d值由2.756nm增大至2.769nm;Mg4Nb2O9陶瓷的微波介电性能随Bi2O3掺杂量增加而变化;掺杂2.0wt%Bi2O3的Mg4Nb2O9陶瓷在1175℃保温2小时烧结,获得亚微米级陶瓷,且具有最佳的微波介电性能,εr为12.58,Q×f为71949.74GHz。     

MgO-B_2O_3二元体系微波介电材料的制备及性能研究

以MgO和B_2O_3为原料,采用固相法合成了0.67MgO-0.33B_2O_3陶瓷。利用X射线粉末衍射仪和阿基米德法研究了烧结温度、烧结时间对陶瓷材料的晶相、介电常数、品质因子Q·f值等性能的影响。结果表明,烧结温度为1 290～1 350℃时,0.67MgO-0.33B_2O_3陶瓷的介电常数并没有显著的变化。当烧结温度在1 350℃以上时,陶瓷则会形成MgO和Mg3B2O6晶相,两相共存;烧结时间对0.67MgO-0.33B_2O_3陶瓷的品质因子Q·f值具有极大的影响;在1 330℃的空气中烧结1h时,得到最高的品质因子Q·f值为270 200GHz,介电常数为7.6。     

Li1.0Nb0.6Ti0.5O3陶瓷的低温烧结其微波介电性能

研究了以Li1．0Nb0．6Ti0．5O3(LNT)陶瓷为基体, B2O3-ZnO-La2O3(BZL)玻璃为烧结助剂的复合材料的低温烧结行为及微波介电特性．研究表明,BZL玻璃能有效降低LNT陶瓷的烧结温度,掺入10wt％BZL玻璃的复合材料能够在900℃烧结致密．XRD与SEM分析结果表明,添加BZL玻璃的样品烧结后含有LNT和LaNbTiO6两种晶相,其中LaNbTiO6相是LNT与BZL玻璃在烧结过程中发生化学反应的产物．在LNT陶瓷中添加BZL玻璃使材料的介电常数和品质因数下降,但有助于减小体系的谐振频率温度系数．掺入10wt％BZL玻璃的复合材料在900℃烧结2h后获得了比较满意的微波介电特性:介电常数k≈58,品质因数Q×f≈4800GHz,谐振频率温度系数τf≈11×10-6／℃．     

(1-x)(Mg0.7Zn0.3)TiO3-xCa0.61La0.26TiO3系陶瓷的微波介电性能研究（英文）

本实验研究了(1-x)(Mg0.7Zn0.3)TiO3-x(Ca0.61La0.26)TiO3(MZT-CLT)系陶瓷的微观结构和微波介电性能,通过(Ca0.61La0.26)TiO3来协调(Mg0.7Zn0.3)TiO3陶瓷的谐振频率温度系数.MZT-CLT陶瓷的主晶相为(Mg0.7Zn0.3)TiO3,第二相为Ca0.61La0.26TiO3和(Mg0.7Zn0.3)Ti2O5.烧结温度和陶瓷组成对微波介电性能影响显著,当烧结温度为1275℃时,可以获得良好的致密度,当烧结温度超过1300℃时,Zn的蒸发导致陶瓷致密度和介电性能下降.随着(Ca0.61La0.26)TiO3含量的增大,材料的介电常数增大,品质因数减小.当x=0.13,烧结温度为1275℃保温4h,(MZT-CLT)陶瓷具有优良微波介电性能,εr=26,Q.f=86000 GHz,τf=-6×10-6/℃.     

添加剂对Y2Ti2O7陶瓷的微波介电性能的影响（英文）

研究了CrO3、Nb2O5、SiO2及Al2O3对Y2Ti2O7陶瓷的烧结性能、相组成和微波介电性能的影响.其中Nb2O5掺杂能够降低Y2Ti2O7陶瓷材料的烧结温度,提高基体陶瓷的介电常数和品质因子,引起谐振频率温度系数的明显变化.且随着Nb2O5含量的增多,所有样品的主晶相仍为立方烧绿石型Y2Ti2O7,Nb5+可能进入烧绿石结构中,部分取代Ti4+所在位置.实验结果表明:1mol%Nb2O5掺杂的陶瓷材料在1420℃下烧结致密,具有最佳的微波介电性能:εr=61.8,Q×f=9096GHz(f=5.494GHz),τf=54×10-6/℃.     

(1-x)(Mg0.9Co0.1)TiO3-x(Ca0.61La0.26)TiO3陶瓷的微波介电性能（英文）

研究了(1-x)(Mg0.9Co0.1)TiO3-x(Ca0.61La0.26)TiO3(MCT-CLT)体系陶瓷的微波介电性能.目的是通过(Ca0.61La0.26)TiO3(CLT)协调(Mg0.9Co0.1)TiO3(MCT)陶瓷的谐振频率温度系数.实验发现,烧结温度和陶瓷组成对微波介电性能影响显著,当烧结温度为1300℃时,可以获得良好的致密度,当烧结温度超过1300℃时,陶瓷致密度和介电性能下降.此外,随着CLT含量的增加,材料的介电常数增大,品质因数减小.当CLT含量为13%,烧结温度为1300℃,保温2h,(MCCLT)陶瓷具有优良微波介电性能,εr=22.4,Q×f=35000 GHz,τf=-8.7×10-6/℃,从而达到实用要求.     

Al2O3掺杂对Ba4Sm9.33Ti18O54陶瓷显微结构和介电性能的影响

采用固相反应法制备了Ba4Sm9.33Ti18O54(简称BST)xwt%Al2O3(x=0~1.5)微波介质陶瓷.研究了掺杂Al2O3对BST陶瓷的显微结构和介电性能的影响.扫描电镜和能谱分析结果显示:未掺杂的BST陶瓷中有少量Sm2Ti2O7相,随着增加Al2O3掺入量,Sm2Ti2O7相消失,BST陶瓷中先后产生了BaTi4O9(x≥0.6)和BaAl2Ti5O14(x≥1.0)两种新相.介电性能测试结果表明Sm2Ti2O7相的消失以及少量BaTi4O9相的形成,能显著提高BST陶瓷的Qf值,但会降低陶瓷的介电常数.当Al2O3的掺入量从0.6wt%增加到1.0wt%时,BaTi4O9相的量逐渐增加,引起BST陶瓷的Qf值略微下降.BaAl2Ti5O14相的产生会同时降低BST陶瓷的介电常数和Qf值.掺入0.6wt%Al2O3的BST陶瓷在1340℃烧结3 h后具有最佳的介电性能:εr=74.7,Qf=10980 GHz,τf=–11.8×10-6/℃.     

Plasma spraying of Al2O3 and Al2O3Y2O3

A microstructural study has been carried out of plasma-sprayed Al₂O₃ and mixed and sintered Al₂O₃Y₂O₃. In order to ascertain the degree of metastability achieved by plasma spraying, these results are compared with a similar experiment utilizing a CO₂ laser for melting and the hammer-and-anvil technique for quenching of the same materials. X-ray diffraction methods were used to determine the obtained phases and crystal structures. In addition, transmission electron microscopy was used to confirm the phases present and to study their morpology. The porosity was studied with both mercury intrusion porosimetry and small angle neutron scattering. The addition of Y₂O₃ is shown to decrease the porosity from 15% to 7.5%. Adhesion is likewise related to the addition of Y₂O₃ and it is seen that adhesion of the mixture is measurably improved over that of pure Al₂O₃. The implication of these results is discussed.     

Surface tension of PbO-B2O3 and Bi2O3-B2O3 glass melts

The surface tensions of xPbO-(100?x) B₂O₃ (x = 30–80 mol%) and xBi₂O₃-(100?x) B₂O₃ (x = 0–100 mol%) melts were measured using the ring method over the temperature range 973 to 1373 K. The compositional and temperature dependences of surface tension were investigated. Addition of PbO and Bi₂O₃ to B₂O₃ increased the surface tensions of their respective PbO-B₂O₃ and Bi₂O₃-B₂O₃ melts. The surface tension showed a maximum at 60 mol% PbO in the PbO-B₂O₃ melts and at 70–80 mol% Bi₂O₃ in the Bi₂O₃-B₂O₃ melts. The temperature coefficient of surface tension was examined on the basis of its relationship to the structure, and it was suggested that the temperature coefficient of surface tension decreases with an increasing content of four-coordinated boron.     

Microstructure and Strength of Al2O3/Al2O3 Joints Bonded with ZnO-Al2O3-B2O3-SiO2 Glass-Ceramic

ZnO-Al2O3-B2O3-SiO2 （ZABS） glass powder was used as interlayer to join alumina ceramics. The effect of joining temperature on the microstructure and strength of joints was investigated. The results showed that the ZABS glass can react with alumina substrate to form a layer of ZnAl2O4 at Al2O3/glass interface. Bending test exhibited that low joining temperature （1150℃） led to low joint strength due to the formation of pores in the interlayer, originated by high viscosity of the glass. High joining temperature （1250 ℃） also resulted in low joint strength, because of large CTE （coefficient of thermal expansion） mismatch between amorphous interlayer and alumina substrate. Therefore, only when the joining temperature was appropriate （1200℃）, defect-free interface and high joint strength can be obtained. The optimum joint strength reached 285 MPa, which was the same as the base material strength.     

Preparation of pressureless-sintered SiC-Y2O3-Al2O3

Sintering additives were prepared from aluminium hydroxide and yttrium hydroxide. These additives were soluble in water and resulted in a binder. A -SiC powder was mixed with the additive solution and sintered at 2150° C without pressure. The oxides formed from the additive promoted sintering. The sintered body contained no pores. Aluminium, silicon, and yttrium oxide were precipitated in the sintered body.     

Some physical properties of V2O5-Fe2O3 and V2O5-Fe2O3-Li2O systems

Various methods have been used to study the physical properties of the V₂O₅-Fe₂O₃ and V₂O₅-Fe₂O₃-Li₂O systems, including X-ray, electron microscope, Mössbauer effect, NMR and thermogravimetric measurements. The iron ions are approximately equally distributed in substitutional and interstitial sites in the V₂O₅ lattice. The maximum number of iron ions dissolved in the V₂O₅ matrix corresponds to 4 mol % Fe₂O₃. In all the samples a quantity of Fe₂O₃ which has not been included in lattice is observed. The V₂O₅-Fe₂O₃ and V₂O₅-Fe₂O₃-Li₂O systems are formed from solid solutions mixed with very small Fe₂O₃ particles. The analysis of the charge compensation of iron ions suggests that V₂O₅ is a quasi-amorphous semiconductor. Irradiation of V₂O₅-based samples with an electron beam induces the V₂O₅ platelets to convert to the VO _x phase.