【作者】 陈亮；

【导师】 方亮； 张辉；

【作者基本信息】 武汉理工大学 ， 材料学， 2005， 硕士

【摘要】 本论文的主要目的是探索新型铌酸盐介电功能材料。随着现代通信技术的高速发展，移动通讯系统的小型化、高频化和集成化发展趋势对研究与开发高性能的新型介电功能材料提出了强烈要求。 本论文首先根据钨青铜结构A₆B₁₀O₃₀的特点，通过氧八面体内、外阳离子的组合设计了Ba₅LnSn₃Nb₇O₃₀（Ln=La，Nd）系列铌酸盐，采用高温固相反应法制备其陶瓷体（两者合成温度1300℃保温12h，最佳烧结温度1350℃保温4h）；通过X射线衍射分析（XRD）、扫描电镜（SEM）形貌分析、密度分析和化学分析进行了表征，确定其属于四方钨青铜结构的纯相。介电性能测试结果表明：在1MHz下Ba₅LaSn₃Nb₇O₃₀、Ba₅NdSn₃Nb₇O₃₀的介电常数（ε_τ）分别是171、182：介电损耗（tan δ）1.2×10^-3、1.8x10^-3；其介电常数的温度系数（τ_ε）较Ba₅LnTi₃Nb₇O₃₀（Ln=La，Nd）有显著下降，有望成为一类新型高介电常数的无铅补偿型介电陶瓷。 然后，根据层状类钙钛矿A₈B₇O₂₄结构特征，在制备了Ba₈Ti₃Nb₄O₂₄陶瓷（合成温度1380℃保温12h，最佳烧结温度1480℃保温4h）的基础上，通过Sr取代A位的Ba，设计并制备了Ba₈-_xSr_xTi₃Nb₄O₂₄（X=1～8）系列陶瓷，结果发现其中含有钙钛矿结构的杂相。微波介电性能测试结果表明，随着Sr对Ba的取代，化合物的介电常数在42.14～75.6之间变化，先增加后降低；品质因子Q·f从9392逐渐降低到2681；谐振频率的温度系数（τ_f）逐渐降低，变化范围为-70～+175 ppm^oC^-1。通过进一步优化，有望从中开发出中、高介电常数的新型微波介质陶瓷材料。更多还原

【Abstract】 The aim of the thesis is to explore and develop promising new niobate dielectric function materials. With the high speed development of modern communication, the trend to miniaturization、 high frequency and integration of mobile communication system intensively requires research and development of new dielectric function ceramics.Firstly, on the basis of the characteristic of filled tungsten bronze structure with the general formula A6B10O30, a series of new niobates Ba5LnSn3Nb7O30 (Ln=La,Nd) were designed in the thesis, and prepared by high temperature solid-state reaction technique (both calcined at 1300℃ for 12h and sintered at 1350℃ for 4h). The ceramics were characterized by X-ray powder diffraction (XRD)、 Scanning Electron Microscope (SEM)、 density analysis and chemical analysis. The dielectric properties of them show that: Ba5LaSn3Nb7O30 and Ba5NdSn3Nb7O30 ceramics have high dielectric constant of 171 and 182 together with low dielectric loss 1.2×10-3 and 1.8×10-3 at 1MHz, respectively. In comparison with dielectric ceramics with TB structure in BaO-Ln2O3-TiO2-Ta2O5 (Ln=La, Nd) system, the temperature coefficients of the dielectric constant (τε) are significantly reduced, and they are promising to be a new type of free lead compensated dielectric ceramics.Then, according to layered perovskite-like structure with the general formula A8B7O24, Ba8Ti3Nb4O24 was prepared (calcined at 1380℃ for 12h and sintered at 1480℃ or 4h). We substituted Ba for Sr at A place, and Ba8-xSrxTi3Nb4O24(x=1-8) were prepared, but they are not pure phases. The result of microwave dielectric testing show that: with substitution of Sr for Ba, dielectric constant (si) of them varies from 42.14 to 75.6, first increase and then fall down; quality factors (Q·f) reduced from gradually from 1976; the temperature coefficients of resonance frequency (τf) reduced gradually in the range of-70-+75 ppm℃-1.It is hopeful to develop some new microwave dielectric ceramics with middle and high dielectric constants from them, if they are optimized.更多还原