【作者】 孟范成；

【导师】 方亮； 张辉；

【作者基本信息】 武汉理工大学 ， 材料学， 2003， 硕士

【摘要】 本论文的主要目的是探索新型钨青铜结构高性能微波介质陶瓷材料和无铅补偿型介电陶瓷。在Ba₅LnTi₃Ta₇O₃₀的基础上，根据钨青铜结构的特点，通过氧八面体内、外阳离子的组合设计，进行了Sr₅LnTi₃Ta₇O₃₀（Ln=La，Nd，Sm，Y）系列钽酸盐陶瓷的制备、结构与介电性能研究。 在化合物可行性理论分析的基础上，采用固相反应法合成了Sr₅LnTi₃Ta₇O₃₀（Ln=La，Nd，Sm，Y）系列钽酸盐陶瓷。通过扫描电镜（SEM）、粉晶X射线衍射（XRD）、化学分析进行了成分与结构分析。获得了其精修的晶胞参数及指标化的X射线粉末衍射数据。结果表明：Sr₅LnTi₃Ta₇O₃₀（Ln=La，Nd，Sm，Y）系列钽酸盐属于四方钨青铜结构。Sr₅LnTi₃Ta₇O₃₀晶胞参数的变化规律与Ln³⁺半径变化相同。 对钽酸盐陶瓷Sr₅LnTi₃Ta₇O₃₀（Ln=La，Nd，Sm，Y；）进行了介电测试，并且分析了Ln³⁺对介电性能的影响。根据介电常数—温度曲线，确定了它们各自的居里温度范围，进一步验证了它们所属的结构类型。实验表明该系列钽酸盐陶瓷的介电特性具有较好的一致性，高频下具有较好的频率稳定性，介电常数随Ln³⁺离子半径不同而变化较小，介电常数小于Ba₅LnTi₃Ta₇O₃₀体系，陶瓷体介电常数的温度系数也小于该体系。 最后，运用Clausius-Mosotti方程结合离子极化率计算了该系列钽酸盐陶瓷的介电常数，计算结果与实测值有较大的偏离。进一步分析认为这一偏离是由于钨青铜结构中氧八面体的畸变及构建形式的不同所导致的。更多还原

【Abstract】 The aim of this thesis is to explore and develop new high dielectric microwave materials as well as free lead compensated dielectric ceramics with tungsten bronze (TB) structure. According to the characteristic of tungsten bronze structure, series of new tantalates Sr5LnTi3Ta7O30 (Ln= La , Nd, Sm, Y) were designed on the basis of Ba5LnTi3Ta7O30 through the substitution of A cation with elements Nd, La ,Sm and Y, respectively. Furthermore, their structure and dielectric properties were studied.Firstly, Sr5LnTi3Ta7O30 (Ln=Nd, La, Sm, Y) compounds were synthesized by high temperature solid state reaction technique and characterized by scanning electron microscope (SEM), x-ray powder diffraction (XRD) and chemical analysis. The results show that the structure of Sr5LnTi3Ta7O30 (Ln=Nd, La, Sm, Y ) belongs to tetragonal tungsten bronze structure.Secondly, the dielectric properties of Sr5LnTi3Ta7O30 (Ln=Nd, La, Sm, Y;) were studied. Through the dependence of dielectric constant vs temperature, Curie temperature (Tc) region and structural phase transitions were determined. The experiment results indicated that the dielectric properties of Sr5LnTi3Ta7O30 (Ln=Nd, La, Sm, Y; ) varied with different Ln , but all of them have high dielectric constants. The temperature coefficients of the dielectric constant(εr) is much smaller compared with that of TB compounds in the Ba5LnTi3Ta7O30 system .Finally, the dielectric constants of Sr5LnTi3Ta7O30 (Ln=Nd, La, Sm, Y; ) were calculated by using Clausius-Mosotti equation with polarizabilities of ions. The calculated values are much smaller than the experimental values. The deviations are worthy to further study.更多还原