0.64BaTi4O9-0.36BaEu2Ti4O12/BaTi4O9纤维复合陶瓷的相结构研究

利用XRD，XPS和TEM等测试手段对0.64BaTi4O9-0.36BaEu2Ti4O12/BaTi4O9纤维复合陶瓷新材料的相结构进行了研究。研究结果表明：随着BaTi4O6纤维的加入，烧结试样表面O元素的含量提高，材料中Ti^3 离子和Ti^2 离子的含量降低，材料介电性能有所提高。     

BaO-TiO2系纤维的合成及BaT4O9纤维复合陶瓷的研究

摘要以水热法合成出BaTi4O9和BaTi5O11两种新型的功能陶瓷纤维,制备了三个体系的BaTi4O9纤维复合陶 瓷新材料,并对其组织结构、介电性能和室温断裂行为进行了研究.论文取得了如下创造性研究成果:(1)合成出以 BaTi4O9和BaTi5O11为主晶相的纤维新材料;对原料K2Ti4O9纤维的形成机制进行了探讨;同时,对中间产物水合二氧 化钛纤维的相变过程进行了研究;(2)成功地制备出BaTi4O9(f)/(0.64BaTi4O9+0.36BaPr2Ti4O12)(简称BPT系列) 和BaTi4O9(f)/()(0.64BaTi4O9+0.36BaEu2Ti4O12)(简称BET系列)两个系列复合陶瓷材料,系统研究了BaTi4O9纤 维的加入量对介电性能的影响,结果表明,含10vol%BaTi4O9纤维的BPT和BET试样具有良好的综合介电性能;(3) 对BaTi4O9纤维和复合陶瓷的组织结构进行了系统研究,揭示了介电性能变化的结构基础,对进一步开发新的相应系 列的微波介质陶瓷材料有重要的参考价值;(4)由纯BaTi4O9纤维制成的试样具有较好的烧结性和介电特性. 关键词微波介质陶瓷纤维复合陶瓷 BaTi4O9纤维介电性能 导师:周玉教授和王福平教授答辩时间:2000-10-19 通讯地址:哈尔滨工业大学2045信箱     

BaTi4O9微波介质陶瓷制备及低温烧结研究进展

微波介质陶瓷作为现代移动通讯中的关键基础材料,以其优异的介电性能已成为现代微波通讯技术的研究重点之一,而BaO-TiO2体系中的BaTi4O9微波介质陶瓷由于具有微波介电性能优异、制备工艺简单以及成本低等优点,已经成为微波介质陶瓷研究领域的热点.从BaTi4O9微波介质陶瓷的结构与性能入手,介绍了BaTi4O9陶瓷的制备工艺、方法及其在器件方面的应用,概述了BaTi4O9微波介质陶瓷在低温烧结方面的研究进展.     

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/℃.     

(Ba1-xSrx)La4Ti4O15（x=0.8～0.95）陶瓷的微结构及微波介电性能研究

采用固相反应法制备了(Ba1-xSrx)La4Ti4O15(x=0.8~0.95)复合体系微波介质陶瓷,并对其进行物相组成、晶体结构分析以及微波介电性能的研究.研究结果表明,(Ba1-xSrx)La4Ti4O15陶瓷主晶相为SrLa4Ti4O15,并伴随有第二相SrLa8Ti9O15.SEM观察表明,Ba0.2Sr0.8La4Ti4O15陶瓷内部微观结构致密,晶粒尺寸在10~20μm之间,晶界清晰.随着x值逐渐增大,(Ba1-xSrx)La4Ti4O15陶瓷中晶粒形态发生变化,气孔增多.在x=0.8时,(Ba1-xSrx)La4Ti4O15陶瓷具有优良的微波介电性能,即εr=40.86,Q×f≈62806 GHz,τf=20×10 6/℃.随着Ba2+的含量逐渐增加,该陶瓷的介电常数εr单调上升,品质因子Q×f值增加,说明适量的Ba2+替代Sr2+能改善陶瓷的微波介电性能.     

Sol-gel法制备BaTiO_3、BaTi_2O_5和BaTi_4O_9粉末

采用Sol-gel法合成了BaTiO3、BaTi2O5和BaTi4O9粉末,利用XRD和SEM研究了它们的晶相和微观结构。在较低温度烧结得到的粉末都存在一定量的杂相,随着烧结温度的升高,杂相逐渐消失。在1000℃以上温度烧结,可以得到单相BaTiO3和BaTi2O5粉末,而单相BaTi4O9粉末则在1300℃以上温度烧结得到。随着n(Ba)/n(Ti)减小,所得单相的烧结温度逐渐升高。随着烧结温度的升高,BaTiO3、BaTi2O5和BaTi4O9粉末的晶粒逐渐长大。800℃以上温度烧结得到的四方BaTiO3钙钛矿相粉末主要由方形和圆形的晶粒组成;1100℃烧结得到的单斜BaTi2O5相粉末主要由近似菱形的晶粒组成;在1200℃烧结得到的正交BaTi4O9相粉末基本由长形的晶粒组成。     

溶胶-凝胶法引入ZnO-2B2O3-7SiO2玻璃对BaO-Sm2O3-4TiO2陶瓷性能的影响

采用固相反应法合成BaO-Sm2O3-4TiO2 (BST)陶瓷粉体.系统研究了溶胶-凝胶法引入ZnO-2B2O3-7SiO2 (ZBS)玻璃对BST陶瓷烧结特性、物相组成、微观形貌及介电性能的影响.结果表明,添加ZBS玻璃的陶瓷试样主晶相仍为类钙铁矿钨青铜结构的BaSm2Ti4O12,次晶相为Sm2Ti2O7.通过溶胶-凝胶法添加6％(质量分数)的ZBS玻璃,可使BST陶瓷的烧结温度从1350℃降低到1050℃,在1050℃烧结3h所得BST陶瓷介电性能优良:εr=60.17,tanδ=0.004,τf=-7.9×10 6/℃.     

Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7陶瓷结构与介电性能的影响

研究了Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(BZN)陶瓷烧结特性、相结构和介电性能的影响.采用传统的固相反应法制备样品,X射线衍射技术分析相结构,SEM观察表面形貌.结果表明,Bi4Ti3O12掺杂能有效地促进烧结,提高介电常数ε,降低介电损耗tgδ,优化介电频率温度系数αε.1000℃烧结8%(摩尔分数) Bi4Ti3O12掺杂的BZN陶瓷具有较好的介电性能ε=192,tgδ= 4.21×10-4,αε=-3.37×10-4/℃.     

CO3O4掺杂Mg2SiO4陶瓷介电性能的研究

采用固相反应法制备了Co3O4掺杂Mg2SiO4微波介质陶瓷,研究Co2+离子掺杂对Mg2SiO4陶瓷烧结特性、相组成和介电性能的影响.结果表明:Co2+可以完全取代Mg2+固溶在Mg2 SiO4晶体中形成(Cox Mg1-x)2SiO4固溶体,通过调整加入的Co3O4的摩尔量可以获得介电性能优良的微波陶瓷.当x=0.025时,在1250℃下保温3h,( Co0.025Mg0.975)2 SiO4陶瓷具有良好的介电性能为:εr=7.7,Q=8850(1.8MHz),电容温度系数为50.4×10-6/℃.     

聚合物分解法合成BaSm 2Ti 4 O 12

以BaCO3、Sm（NO3）3及Ti（OC4H9）4为原料，采用柠檬酸盐前驱体法制备BaSm2 Ti4O12并与草酸盐共沉淀法制备BaSm2 Ti4O12粉体过程作了比较．结果发现，利用聚合物分解法，可以在1000℃的较低温度下得到单相结晶的BaSm2 Ti4O12，而草酸盐沉淀法则需要1300℃的高温才能合成纯的BaSm2 Ti4O12相．研究表明，这两种液相法所需合成温度相差很大，是由于不同的相演化过程及反应步骤所致．在共沉淀法中，当煅烧前驱体时，中间相Sm2 Ti2O7与BaTi4O9和BaTiO3反应生成BaSm2 Ti4O12相，其过程与固相法相类似．而在聚合物分解法中，前驱体在热分解过程中生成BaTi2O5相，导致了与固相过程完全不同的反应机制，促进了BaSm2 Ti4O12相的形成．     

Dielectric properties of BaTi4O9 single crystals

The barium tetratitanate (BaTi₄O₉) single crystals grown in a nitrogen gas by the floating zone method was characterized by dielectric property in the frequency range 1 kHz to 1 MHz. The as-grown crystals had an electric behaviour such as shown by a semiconductor. When the crystals were annealed at 1300° C for 5 h in air, the dielectric constant was independent of the frequencies and was anisotropic, and theQ-value became higher than that of the grown crystals. Further, from electron spin resonance measurements it was found that the as-grown crystals contained the Ti³⁺ ion. This seems to suggest that the electrical conductivity of the as-grown crystals is due to the Ti³⁺-Ti⁴⁺ hopping mechanism.     

Properties of Mn-doped BaTi4O9-ZnO-Ta2O5 ceramics

In Part I, the reaction sequence, microstructural analysis and microwave dielectric properties of manganese-doped BaTi₄O₉ + ZnO + Ta₂O₅ ceramics are discussed. This composition undergoes complex intermediate reactions during calcination. However, the final crystal phases after the sintering process were identical regardless of calcination temperature. Meanwhile, different calcination temperatures affect the relative volume fractions of the BaZn₂Ti₄O₁₁ phase and result in variations in T _f values. To analyse the microstructure, SEM, TEM and EDS analysis were performed. Mn dopants greatly enhanced the Q factor, up to 11000 at 4.5 GHz, whereas undoped ceramics indicated a high loss, probably due to the formation of Ti³⁺ during sintering in air.     

水热法制备BaTi4O9纤维

通过水热法首次制备了微波介质材料－－ＢａＴｉ４Ｏ９的纤维体。对由此方法制得的钡钛纤维前驱全在７５０－１０００℃温区范围内进行了煅烧合成实验，通过Ｘ衍射定向分析表明：在７５０℃保温２小时的合成条件下，开始出现ＢａＴｉ４Ｏ９；在１０００℃保温２小时的合成条件下，可获得ＢａＴｉ４Ｏ９为主晶相的纤维。     

四钛酸钡纤维陶瓷的制备及介电性研究

首次制备了BaTi4O9纤维陶瓷新材料。利用XRD分析烧结前后试样的相组分变化并在SEM和TEM下观察分析试样的微观结构。初步研究了材料的介电性能。     

Microwave characteristics of mixed phases of BaTi4O9-BaPr2Ti4O12 ceramics

The microwave characteristics of the BaTi₄O₉-BaPr₂Ti₄O₁₂ system were investigated, including its microstructure and infrared reflection spectroscopy. It was found that this system is entirely composed of two phases, BaTi₄O₉ and BaPr₂Ti₄O₁₂, and it is suggested that the lattices of each phase are well matched obliquely at the interface in the sintered ceramics. The dielectric properties are compared with calculated values deduced from the mixing relations of the two components. Furthermore, the infrared reflection spectra of this system were analysed with the factorized form of the dielectric function, for the purpose of studying the applicability of the reflection analysis technique to this mixed phase system.     

Thermal processing and properties of BaTi4O9 and Ba2Ti9O20 dielectric resonators

Sn-doped and undoped barium titanates pressed powder pellets were sintered at 1360 and 1390°C for 5 h. Though batched to form Ba₂Ti₉O₂₀, a two-phase microstructure of BaTi₄O₉ and TiO₂ formed from the undoped system. The dielectric constant at 6 GHz was 40 without SnO₂ additions. Doping with 1.64 mol % SnO₂ stabilized Ba₂Ti₉O₂₀ and formed a single-phase microstructure but resulted in higher porosity. Dilatometry studies implied that SnO₂ additions facilitated a greater fraction of reaction to occur in the solid state, causing a lower quantity of pore-filling fluid to form above 1317°C. As a result of the higher porosity, the dielectric constants and quality factors were also reduced.