【作者】 黄彩清；

【导师】 肖汉宁；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2008， 硕士

【摘要】 ZnO是一种具有宽能隙的半导体材料,其非常优异的非线性电流-电压特性被用来制备压敏电阻片,并广泛应用于电子特别是高压电力行业,以保护电气装置免受浪涌冲击。作为避雷器的核心部件,ZnO压敏电阻片性能水平的高低直接影响着高压输变电系统的安全性和可靠性。随着特高压大容量输变电工程的发展,作为雷电和过压保护装置的避雷器的安全性、可靠性和小型化的要求越来越高,ZnO避雷器逐渐取代了其它传统避雷器而成为新一代高压浪涌避雷器。为了更好地满足高压电力发展的要求,开发具有高电位梯度和大过流容量的ZnO压敏电阻片成为国内外开发氧化锌避雷器的技术关键。虽然对该问题已有大量研究报道,但并没有多少研究成果得到实际应用少。为了进一步改善ZnO压敏电阻片的电性能并保证其实用性,本文通过烧结工艺和材料组成的优化,系统地研究了各种因素对ZnO压敏电阻片显微结构和电性能的影响,探讨了颗粒生长及传导机理,并且采用共烧结法制备了稀土、氧化铟玻璃掺杂ZnO压敏电阻片,提高了ZnO压敏电阻片的电位梯度和非线性系数。研究了烧结工艺对ZnO压敏电阻片的影响。通过对烧结行为的研究,发现升温速度和烧结温度是影响电阻片显微结构和电性能的两个主要因素。当升温速率从200℃/h下降到50℃/h时,电阻片的电位梯度逐渐升高同时泄漏电流逐渐减小。该现象表明在ZnO压敏电阻片的烧结过程中,需要慢速升温以保证传质彻底而形成理想的微观结构。在1030℃下烧成的电阻片具有最好的综合电性能。研究了不同的稀土氧化物掺杂对ZnO压敏电阻片的影响。与掺杂Er₂O₃的ZnO电阻片相比,掺杂了Y₂O₃的电阻片具有更高的电位梯度和非线性系数。在Y₂O₃掺杂量为0.2⁰.8mol%范围内,随着Y₂O₃掺杂量的增加,ZnO压敏电阻片的电位梯度和非线性系数增大;泄漏电流减小。Y₂O₃的掺杂量为0.6mol%时,ZnO压敏电阻片的综合电性能最佳。进一步增加Y₂O₃含量时,ZnO压敏电阻片的电位梯度逐渐下降,泄漏电流逐渐增大。采用共烧结法制备了ZnO-Y₂O₃-In₂O₃玻璃电阻片。该种电阻片不仅克服了ZnO-Bi₂O₃基电阻片中Bi₂O₃易挥发以及ZnO-Pr₆O₁₁基电阻片中Pr₆O₁₁价格昂贵的缺点,而且避免了制备烧结前驱体的复杂步骤。在1020℃的低温下烧成的ZnO-Y₂O₃-In₂O₃玻璃电阻片具有比其它系统更优异的电性能,添加了SnO₂的ZnO-Y₂O₃-In₂O₃玻璃电阻片的平均电位梯度达到了552V/mm,非线性系数达到了47。更多还原

【Abstract】 Zinc oxide, as a wide band-gap semiconductor material, is utilized in varistors. The zinc oxide based varistors are widely used in electric appliances especially in high voltage lines as voltage surge protection devices. Owing to the excellent nonlinear current-voltage characteristics, zinc oxide based varistors become the core elements of the arrester and directly affect the security and the reliability of the power lines.At present, the rapid development of super high-voltage power net-work makes the pressing requirement for the arrester with more security, reliability and miniaturization. Owing to the zinc oxide surge arrester possessing excellent properties of high voltage gradient and energy absorption capability, it becomes the most famous modern high-voltage surge arrester. To make a further improvement in electric properties of zinc oxide based varistor, a systematic research had been carried out by optimizing the sintering process as well as the compositions of the additives. Various influencing factors, such as the sintering condition, dopant species and doping content, on the microstructural and electrical properties were investigated. Otherwise, the growth mechanism of crystals was discussed.The sintering behaviors of the ZnO varistor were investigated, and the influence of heating rate and sintering temperature on the electric properties of the ZnO varistor were studied. With the decrease of heating rate from 200℃/ h to 50℃/ h, the varistor voltage increased and the leakage current decreased. It suggests that lower heating rate is necessary to form an optimal microstructure for obtaining the superior electric properties. The varistor sintered at 1030℃exhibits the higher varistor voltage and lower leakage current.The ZnO varistor doped with various rare earth oxides were studied. The Y₂O₃ doped ZnO varistors exhibit higher varistor voltage as well as the nonlinear coefficient. As the amount of the rare earth oxides increased, the water absorption and leakage current decreased whereas the varistor voltage and nonlinear coefficient increased. When the amount of Y₂O₃ increased to 0.6 mol%, the ZnO varistor achieved the optimum varistor voltage of 505V/mm.A ZnO-Y₂O₃-In₂O₃ glass based varistor was prepared by the method of direct co-sintering synthesis of oxides. This kind of varistor not only overcomes the drawback of large Bi₂O₃ volatilization in ZnO-Bi₂O₃ based varistor, but also avoids the high price of Pr₆O₁₁ in ZnO-Pr₆O₁₁ based varistor. Moreover, ZnO-Y₂O₃-In₂O₃ glass based varistor exhibits more excellent electric properties compared with other systems. It has an average varistor voltage up to 552V/mm, nonlinear coefficient up to 47.更多还原