【作者】 洪秀成；

【导师】 肖汉宁； 成茵；

【作者基本信息】 长沙理工大学 ， 材料学， 2009， 硕士

【摘要】 ZnO压敏电阻片是以ZnO为主要成分,添加某种压敏形成剂(如Bi₂O₃和Pr₆O₁₁)以及其他多种金属氧化物,经高温烧结而成的半导体陶瓷,在高压输变电线路、城市地铁和电气化铁路接触网系统中应用广泛。高性能ZnO压敏电阻片作为ZnO避雷器的核心部件,其性能及制造技术直接制约着ZnO避雷器的发展。因此,提高ZnO压敏电阻片的性能是高压电网系统中加强对雷电浪涌防护的重要研究课题。本文通过稀土氧化物掺杂进行成分优化,制备高压输变电用Bi₂O₃系ZnO压敏电阻片,探讨了不同烧结工艺下的晶粒生长动力学,并研究开发新型Pr₆O₁₁系ZnO压敏电阻片以改善Bi₂O₃系压敏电阻片添加物多、Bi₂O₃易挥发及高电阻抗性等缺点。在稀土氧化物掺杂量为0.2⁰.8mol%范围内,探讨了稀土氧化物（Y₂O₃、Er₂O₃）及掺杂量对Bi₂O₃系ZnO压敏电阻片微观结构和电性能的影响,得出最佳的稀土氧化物及其掺杂区间。实验结果表明:掺杂0.6mol%Y₂O₃时,试样的综合性能最佳,其性能指标分别为:电位梯度:505V/mm;非线性系数:29.6;漏电流:345μA。研究了Y₂O₃掺杂ZnO-Bi2O3压敏电阻片晶粒生长动力学。实验结果表明:试样的平均晶粒尺寸,随着烧结温度的提高和烧结时间的延长而长大。当掺杂0.6mol% Y₂O₃的ZnO压敏电阻片在1030℃下烧结保温2h后,试样的平均晶粒尺寸最小,约为1.5μm;1070℃下烧结保温8h的试样平均晶粒尺寸最大,约为4.2μm。根据晶粒生长动力学方程,计算得到掺杂0.6mol%Y₂O₃的ZnO-Bi₂O₃压敏电阻片的晶粒生长动力学指数n=4,晶粒生长活化能Q=1182kJ/mol。探讨了添加不同CeO2含量对Pr₆O₁₁系ZnO压敏电阻片显微结构及电性能的影响,以期能满足特高压输变电用高电位梯度的应用需求。结果表明:随着CeO₂掺杂量的增加,ZnO-Pr₆O₁₁系压敏电阻片电位梯度和非线性系数有明显的提高,在掺杂量为1.0mol%时达到峰值,分别为548V/mm和42。XRD、SEM检测分析表明:CeO2并不与ZnO及其他氧化物生成新相,而是以CeO₂的形式独立存在,抑制了（Zn_i）^·的生成,致使填隙锌离子的传质能力下降,从而减小ZnO晶粒尺寸,并改善了压敏电阻片的晶界结构和成分。讨论了Pr₆O₁₁系ZnO压敏电阻片的球磨、模压成型、烧结过程的影响因素。研究发现:本体系ZnO压敏电阻材料的球磨工艺应采用无水乙醇作球磨液体介质,不宜采用蒸馏水。采用两次先后加压、适当减小成型压力以及增加保温时间可以减少压制过程中出现的层裂现象。50℃/h的烧结速度比较理想,烧结后的试样气孔较少。更多还原

【Abstract】 ZnO varistor （variable resistors） is a sintered ceramic semiconductor device based on ZnO combined with varistor-forming oxides, such as Bi₂O₃ and Pr₆O₁₁, and a number of other metal oxides, ZnO varistors are widely used in high-voltage transmission lines, urban metro lines and rail network systems.High-performance ZnO varistor as a core component of ZnO surge arresters, its properties and manufacturing process directly restricts the development of ZnO surge arresters. Improving the performance of ZnO varistors is an important research topic for the grid system to enhance lightning surge protection. In this thises, the effect of rare earth oxides doped in Bi₂O₃- ZnO varistors on the constituents prepareing high-voltage ZnO varistors were investigated. The grain growth kinetics under the different sintering conditions was discussed. The development of new Pr₆O₁₁- ZnO varistors is expected to overcome the high volatility and reactivity of Bi₂O₃.The effect of the rare earth oxide （Y₂O₃, Er₂O₃） doped with 0.2 0.8mol% on the microstructure and electrical properties of ZnO-Bi₂O₃ has been investigated. It is aim to obtain the most optimum rare earth oxides and doping. The results show that: When the amount of Y₂O₃ increased to 0.6mol%, the ZnO varistor achieved the optimum electrical characteristics: V1mA/d=505V/mm;α=29.6; IL=345μA.The grain growth kinetics of Y₂O₃-doped ZnO-Bi₂O₃ varistors has been studied. The results show that: with the increase of sintering temperature and sintering time, the average grain size of samples growed up. When doped with 0.6mol% Y₂O₃, sintered at 1030 oC for 2h, the average grain size of ZnO varistors gain the smallest, about 1.5μm; whereas largest about 4.2μm at 1070 oC sintered for 8h. According to grain growth kinetics equation, 0.6mol% Y₂O₃-doped ZnO-Bi₂O₃ varistors have the grain growth kinetics of index n = 4, grain growth activation energy Q = 1182kJ/mol.In order to discuss the feasibility of ZnO-Pr₆O₁₁ varistors used in the fields of high-voltage power transmission. The microstructure and electrical properties of ZnO-Pr₆O₁₁ varistors doped with various amount of CeO2 have been investigated in this article. The resualts of experiment indicate that adding CeO₂ would greatly increase the threshold voltage and the nonlinear coefficient of the ceramics, whereas the leakage current is almost unchangeable. When the amount of CeO₂ increased to 1.0mol%, the ZnO varistor achieved the optimum electrical characteristics, the threshold voltage reaches 548V/mm and the nonlinear coefficient is 42. The SEM and XRD analyses testify that the microstructure of CeO2-doped ZnO-Pr₆O₁₁ varistor ceramics was composed of ZnO grain and intergranular layer: Pr₆O₁₁、Pr₂O₃ and CeO₂ phases only. The grain size of ZnO is diminished by Zni·, which is controlled by the amount of CeO₂. It also improves the structure and component of grain boundary.The effect factors of milling, molding process and sintering in ZnO-Pr₆O₁₁ Varistors was discussed. The results indicate that the system ZnO varistor material milling process should be used for milling ethanol liquid medium, should not use distilled water. Twice successively with pressure, reduce the molding pressure and increase the appropriate holding time can be reduced to suppress the process of spall fracture occurs. The ideal heating rate is 50 oC, when the pore is lowest in the sintered samples.更多还原