摘要钛酸锶钡基铁电陶瓷因其良好的介电性能及居里温度可调而被广泛关注。但其铁电-顺电相变温区狭窄引起介电常数温度稳定性差限制了它在温度稳定型电容器陶瓷领域的应用。

本论文研究了采用传统固相法制备的非化学计量(Ba0。75Sr0。25)Ti1+δO3体系中不同La2O3掺杂量、烧结工艺及成型压力对体系微观结构和介电性能的影响。实验发现：(Ba0。75Sr0。25)Ti1+δO3体系随着δ取值增大居里峰发生移动，适当的非化学计量比有利于降低该钛酸锶钡体系的室温介电损耗，并提高了介电常数及损耗的温度稳定性。在Ba0。75Sr0。25Ti1。006O3体系陶瓷中掺入稀有金属氧化物La2O3的实验发现：La2O3掺杂量对Ba0。75Sr0。25Ti1。006O3陶瓷的微观结构有较大影响，在一定程度上增加掺杂量可以使粒径分布相对均匀，而且掺杂较多时(1。6wt%)能够抑制晶粒的长大，有利于获得细晶结构；其介电常数、损耗及电阻率均与掺杂量关系密切，并且随着掺杂量的增大，居里峰逐渐向低温段移动；另外不同烧结保温时间及粉料成型压力对陶瓷性能的影响也十分显著。87089

毕业论文关键词：陶瓷；非化学计量；La2O3；介电性能；成型压力

Abstract Barium strontium titanate ceramics have been widely concerned for the high dielectric constant and changeable Cure-temperature。 While their disappointing dielectric temperature stability caused by the narrow ferroelectric-paraelectric phase transition temperature zone limits its application in the field of temperature-stable ceramic capacitor。

The nonstoichiometric Ba0。75Sr0。25Ti1+δO3 system capacitor dielectric ceramics prepared by the conventional solid state method were synthesized by adding different content of La2O3, calcining progress and molding pressure to study the effects on the microstructures and dielectric properties。 Results show that the Curie temperature of Ba0。75Sr0。25Ti1+δO3 system ceramics shifts to lower temperature range with the increase of La2O3 doping amount, and suitable nonstoichiometric scale can reduces the room tempereture dielectric loss and promote the temperature stability of the ceramics’ dielectric constant and lose。 A series of experients that joined La2O3 into Ba0。75Sr0。25Ti1。006O3 ceramics indicate that the content of La2O3 affects the ceramics’ microstructures a lot, and if we add more La2O3 properly the uniformity of grain diameter’ distribution would be improved。 What’s more, having increasing the content of La2O3(1。6wt%) has reducd the grain size and acquired fine-grained structure in the last。 Their insulation resistivity in room temperature, dielectric constant and lose change obviously in different content of La2O3, and the Curie temperature goes to lower temperature gradually when the content increases。 In addition, we studied the connection between dielectric properties and experiment parameters including molding pressure and sintering time。 We found that there was a intimate relationship between them。

Keywords: ceramics; nonstoichiometry; La2O3; dielectric properties; pressure

目  录

第一章 绪论 1

1。1 前言 1

1。2 稀土相关知识 2

1。2。1 稀土元素及其性质 2

1。2。2 稀土在功能陶瓷中的运用 3

1。3 钛酸锶钡(BST)的简介 3

1。3。1 电容器陶瓷简介 3

1。3。2 铁电陶瓷简介 4

1。3。3 钛酸锶钡材料的结构 5