氧化锌复合导电陶瓷的制备与性能表征

发布时间：2018-06-10 11:17

本文选题：氧化锌复合导电陶瓷 + 组成　；参考：《陕西科技大学》2017年硕士论文

【摘要】：氧化锌复合导电陶瓷是一类在电力电子工业具有广泛应用前景的功能材料。长期以来,由于制备工艺和理论研究的不足,严重制约了这类材料的工业化生产。本文以ZnO-ZnAl_2O_4-Mg O为基础体系,深入探讨了基体组成以及烧结温度对于其显微结构和电学性能的影响规律,成功制备出了一类可用于高频电场、综合性能较优的新型氧化锌复合导电陶瓷。文章首先探讨了基体组成对于氧化锌复合导电陶瓷显微结构和电学性能的影响规律。结果发现:当Mg O的含量为5.00 mol%、烧结温度为1320 o C时,通过改变ZnAl_2O_4的含量,可以制备出临界频率高于0.67 M Hz、非线性系数在0.99~1.23范围内、电阻率在11.60~123.48W·cm范围内连续可调的氧化锌复合导电陶瓷。考虑到工业生产过程中Zr4+可能被引入基体,本文在性能较优的三元基础体系中研究了ZrO_2掺杂的影响规律。结果发现:掺杂少量的ZrO_2有利于微观形貌和电学性能的优化。当ZrO_2含量为0.30 mol%、烧结温度为1320 o C时,试样的电阻率为19.59W·cm、非线性系数为1.01、阻温系数为-2.60′10-3/o C、临界频率为1.20 M Hz。为了克服试样在致密性以及对烧结温度敏感等方面的不足,本文在性能较优的基础体系中引入NiO相进行改性。结果发现:NiO的添加可以降低烧成温度,显著改善试样的致密性。当NiO含量为7.00 mol%、烧结温度为1280 o C时,可以获得性能较优的四元体系氧化锌复合导电陶瓷,其电阻率为15.13W·cm、非线性系数为1.05、阻温系数为-1.79′10-3/o C、临界频率为1.25 M Hz。此外,Ni2+在ZnO晶格中的固溶可以降低烧结过程中坯体内的温度梯度,从而显著地降低了试样对烧结温度的敏感性。在研究烧结温度对于试样电学性能影响的过程中,本文选择了1280 oC~1400 o C的温度区间。结果发现:烧结温度对于氧化锌复合导电陶瓷的电学性能产生了显著影响。温度升高可以促进致密化过程、引起晶粒和晶界电阻率的显著降低。与此同时,温度升高可以削弱界面效应,引起非线性系数的降低和临界频率的提高。但是过高的烧结温度温度可能会破坏试样显微结构的均匀性,造成电学性能的劣化。同时,由于在氧化锌复合导电陶瓷中,晶界势垒较低、不具有活性,因此试样能够呈现出线性伏安特性和高频稳定特性。此外,氧化锌复合导电陶瓷的导电机理符合“热激发”和“渗流导电”模型,基体中存在显著的Maxwell-Wagner界面极化,这种极化方式维持了稳定的晶界效应。
[Abstract]:Zinc oxide composite conductive ceramics is a kind of functional materials with wide application prospect in power electronics industry. For a long time, the industrial production of this kind of material has been restricted seriously because of the shortage of preparation technology and theoretical research. In this paper, based on ZnO-ZnAl2O4-MgO system, the effects of matrix composition and sintering temperature on microstructure and electrical properties of ZnO ZnAl2O4-MgO system are discussed. A class of high frequency electric fields have been successfully prepared. New type zinc oxide composite conductive ceramics with better comprehensive properties. In this paper, the effect of matrix composition on microstructure and electrical properties of ZnO composite conductive ceramics is discussed. The results show that when the content of MgO is 5.00mol / L and the sintering temperature is 1320 oC, the critical frequency is higher than 0.67m Hz and the nonlinear coefficient is in the range of 0.991.23 by changing the content of ZnAl2O4. Zinc oxide composite conductive ceramics with continuously adjustable resistivity in the range of 11.60 ~ 123.48 W cm. Considering that Zr4 may be introduced into the matrix during industrial production, the effect of ZrO _ 2 doping in ternary basic system with better performance has been studied in this paper. The results show that doped with a small amount of ZrO _ 2 is beneficial to the optimization of micromorphology and electrical properties. When the content of ZrO2 is 0.30mol / L and the sintering temperature is 1320 OC, the resistivity is 19.59W / cm, the nonlinear coefficient is 1.01and the resistance temperature coefficient is -2.60,10-3 / oC, and the critical frequency is 1.20mHz. In order to overcome the shortage of densification and sensitivity to sintering temperature, nio phase was introduced into the basic system with better properties. The results show that the addition of w / nio can decrease the sintering temperature and improve the densification of the samples. When the nio content is 7.00 mol / L and sintering temperature is 1280 o C, the quaternary ZnO composite conductive ceramics with better properties can be obtained. The resistivity is 15.13 W / cm, the nonlinear coefficient is 1.05, the resistance temperature coefficient is -1.79 / 10 ~ (-3) / o _ (C), and the critical frequency is 1.25m Hz. In addition, the solid solution of Ni2 in ZnO lattice can reduce the temperature gradient of the billet during the sintering process, thus significantly reducing the sensitivity of the sample to the sintering temperature. In the course of studying the influence of sintering temperature on the electrical properties of the sample, the temperature range of 1280 OC / 1400oC is selected. The results show that the sintering temperature has a significant effect on the electrical properties of ZnO composite conductive ceramics. The increase of temperature can promote the densification process and cause the decrease of grain size and grain boundary resistivity. At the same time, the increase of temperature can weaken the interfacial effect and cause the decrease of nonlinear coefficient and the increase of critical frequency. However, too high sintering temperature may destroy the uniformity of microstructure and result in deterioration of electrical properties. At the same time, because the grain boundary barrier is low and the sample is not active in ZnO composite conductive ceramics, the sample can exhibit linear voltammetry and high frequency stability characteristics. In addition, the conductive mechanism of ZnO composite conductive ceramics accords with the "thermal excitation" and "percolation conduction" models, and there is a significant Maxwell-Wagner interfacial polarization in the matrix, which maintains a stable grain boundary effect.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.1

【参考文献】