摘 要

向SrTiO₃陶瓷中掺杂Ca² 可以有效改善陶瓷的显微结构以及介电、击穿场强等性能，但是目前研究Ca² 掺杂SrTiO₃陶瓷的报道很少。本论文主要研究了Sr_1-xCa_xTiO₃陶瓷因Ca² 掺杂量以及烧结气氛等的不同而产生的结构与性能的变化情况，所得结果对于系统地研究Ca² 掺杂对SrTiO₃陶瓷的改性具有重要意义。所以本论文的主要工作包括：

（1）采用常规固相反应法制备了Sr_1-xCa_xTiO₃陶瓷（x=0.5mol%，1.0mol%，1.5mol%，2.0mol%，4.0mol%，8.0mol%），并分别在空气气氛和N₂气氛中进行烧结，对空气中烧结的样品进行了物相结构、显微结构、介电性能和击穿场强等性能的测试，研究了不同Ca² 掺杂量对其结构和性能的影响；对N₂中烧结的样品进行了显微结构和介电性能的测试，并将其与空气中烧结样品的测试结果进行比较与分析。

（2）陶瓷的结构测试结果表明，Sr_1-xCa_xTiO₃陶瓷均为单相结构，说明实验中的CaTiO₃在SrTiO₃中具有较大的固溶度，可以推断其形成了连续置换固溶体。在空气中烧结的样品随着Ca² 掺杂量的增加平均晶粒减小，但是在N₂中烧结的样品晶粒尺寸逐渐增大，并且均小于空气中烧结的样品，表明气氛烧结对陶瓷的微观结构有明显的改善作用。

（3）陶瓷性能测试结果显示，在空气中烧结的Sr_1-xCa_xTiO₃陶瓷的Ca² 掺杂量从0.5mol%增加到8.0mol%，其室温介电常数呈现出逐渐增大的趋势，最大达到328（x=8.0mol%），Ca² 掺杂量x=0.5mol%，1.0mol%，1.5mol%，2.0mol%，4.0mol%的Sr_1-xCa_xTiO₃陶瓷介电常数从290增大到323，并且介电损耗都小于0.1。耐电场强度的测试结果表明x=4.0mol%时陶瓷的击穿场强最高，达到314.2 kV/cm，通过介电常数和击穿场强的数值计算得到的陶瓷有效储能密度在x=4.0mol%时达到最大值，约为1.1 J/cm³。在N₂气氛中烧结的Sr_1-xCa_xTiO₃陶瓷常温下的介电常数相对于空气中烧结的陶瓷没有出现明显增大的现象，基本都为290左右，但是其介电损耗则维持在0.01以下，明显小于空气中烧结的陶瓷，并且与空气烧结的陶瓷样品相似，在100 Hz～1 MHz的频率范围内也具有明显的介电弛豫特征。

关键词：Sr_1-xCa_xTiO₃陶瓷；Ca² 掺杂量；气氛烧结；结构与性能

Abstract

Ca-doped SrTiO₃ ceramics have superior microstructure, dielectric properties, breakdown strength (BDS) and other properties compared with SrTiO₃ ceramics. Currently, reports of studying Ca-doped SrTiO₃ ceramics are very few. Here, the changes of structure and properties of Sr_1-xCa_xTiO₃ ceramics due to different doping and sintering conditions of the atmosphere are studied mainly. The results of studies are very important for systematic study of modifying to doping Ca² in SrTiO₃ ceramics. Therefore, the following work was carried out:

(1) The Sr_1-xCa_xTiO₃ ceramics (x=0.5mol%,1.0mol%,1.5mol%,2.0mol%,4.0mol%,8.0mol%) have been synthesized by conventional solid state reactions, and they were sintered in an air atmosphere and atmosphere of N₂ respectively. The phase structures, micro-structure, dielectric properties and BDS of Sr_1-xCa_xTiO₃ ceramics sintered in an air atmosphere have been tested, and the influence of doping of Ca² to the structure and properties of SrTiO₃ ceramics was analyzed. In addition, the micro-structure and dielectric properties of samples sintered in N₂ atmosphere were studied and compared with the consequent of the ones sintered in air atmosphere.

(2) The results of structure examination show that the ceramics were single-phase structure, which exhibits that CaTiO₃ has a big solubility in SrTiO₃ ceramics and the conformation of continuous substitution solid solution can be inferred. When the doping of Ca² increased, the average grain of the samples sintered in air were reduced, but that sintered in N₂ were increased and smaller than the samples sintered in air. It suggests that sintered in N₂ can efficiently improve the micro-structure of ceramics.

(3) The results of properties examination show that with the doping of Ca² in Sr_1-xCa_xTiO₃ ceramics sintered in air increased from 0.5mol% to 8.0mol%, the dielectric constant at room temperature showed an increasing trend. The maximum was 328 (x=8.0mol%), and the dielectric constant of Sr_1-xCa_xTiO₃ ceramics (doping of Ca² was x=0.5mol%, 1.0mol%, 1.5mol%, 2.0mol%, 4.0mol%) changed from 290 to 323, and the dielectric loss were less than 0.1. According to the results of BDS test, the maximum of samples was 314.2 kV/cm when x=4.0mol%. And the highest energy density calculated by using dielectric constant and BDS was about 1.1 J/cm³ with doping of Ca² was 4.0mol%. The dielectric constant at room temperature of Sr_1-xCa_xTiO₃ ceramics sintered in N₂ were similar to the samples sintered in air, but the dielectric loss were less than 0.01 and obviously less than the latter. Moreover, it is found that dielectric relaxation behavior existed in either the samples sintered in air atmosphere or in the ones sintered in N₂ atmosphere in the range of frequency from 100 Hz to 1 MHz.

Key Words：Sr_1-xCa_xTiO₃ ceramics; doping of Ca² ; sintered in different atmosphere; structure and properties

目 录

摘 要 I

Abstract II

第1章 绪论 1

1.1 电介质简介和电介质的极化与击穿 1

1.1.1 电介质材料简介 1

1.1.2 介电常数与电介质的极化 1

1.1.3 电介质的击穿与击穿场强 2

1.2 SrTiO₃基氧化物陶瓷材料的研究现状 3

1.2.1 功能陶瓷材料简介 3

1.2.2 SrTiO₃基陶瓷材料的研究 3

1.3 本文研究的目的与内容 4

1.3.1研究的目的与意义 4

1.3.2 实验的主要内容 4

第2章 Sr_1-xCa_xTiO₃陶瓷制备及其结构和性能表征 6

2.1 实验药品及设备 6

2.2 Sr_1-xCa_xTiO₃陶瓷的制备工艺 7

2.3 Sr_1-xCa_xTiO₃陶瓷的结构及性能表征方法 8

2.3.1 体积密度测试 8

2.3.2 X射线衍射测试（XRD） 9

2.3.3 扫描电子显微镜测试（SEM） 9

2.3.4 介电常数温度和频率依赖性测试 9

2.3.5 耐电压强度测试 10