【作者】 严群；

【导师】 涂铭旌；

【作者基本信息】 四川大学 ， 材料学， 2003， 博士

【摘要】 本文通过添加微量稀土和部分纳米级粉料提高氧化锌压敏阀片的压敏性能，研究纳米级粉料对氧化锌压敏阀片性能的影响规律及机理，并首次系统地研究稀土氧化物对氧化锌压敏阀片性能的影响机理，使氧化锌避雷器阀片的性能在保证通流能力及泄漏电流基本保持不变的条件下，其压敏电位梯度大幅度提高，实验室样品结果达到550V／mm以上，以期在工程应用中达到甚至超过国外400V／mm的先进水平，较之国内200V／mm的普通水平提高100％甚至以上。 首先研究了烧结工艺对氧化锌压敏阀片几种主要电气性能的影响，对烧结工艺进行了筛选和优化。研究结果表明，氧化锌压敏阀片的最佳烧成制度为：随炉连续缓慢升温至1150℃进行烧结，保温2.5小时后，随炉缓慢冷却。 在传统配方的氧化锌压敏阀片原料中添加微量稀土氧化物Nd₂O₃、CeO₂、La₂O₃，研究各种稀土氧化物的添加量对氧化锌压敏阀片主要电性能的影响规律，优化氧化锌压敏阀片原料中稀土氧化物的添加量。研究结果表明，三种稀土添加剂中，Nd₂O₃提高压敏电位梯度的作用最为显著，La₂O₃次之，CeO₂最弱，而且当Nd₂O₃的含量为0.04 mol％时，压敏阀片的三个主要电性能指标都达到最佳值（电位梯度最高约达583.25V／mm，漏电流小，压比低），而添加La₂O₃或CeO₂的压敏阀片的三个主要电性能指标最佳值所对应的成分却并不一致，因此适量的Nd₂O₃显著提高压敏电位梯度的同时，可降低漏电流四川大学博士学位论文和压比，使压敏阀片具有优良的综合电性能。 在传统配方的氧化锌压敏阀片原料中添加一定量的纳米氧化锌，研究纳米氧化锌的添加量对压敏阀片主要电性能的影响规律，优化压敏阀片原料中纳米氧化锌的添加量。研究结果表明，压敏阀片中加入纳米氧化锌后，其压敏电位梯度显著提高，当纳米ZnO含量达到SOwt%时，压敏电位梯度可达613.73vlmm。纳米氧化锌的添加量为10wt%时，压敏电位梯度较高，漏电流最小，压比较低，即压敏阀片的综合电性能较好。 运用扫描电镜（SEM）、能谱仪（EPO）、X射线衍射仪（XRO）、显微图像分析系统对试样进行显微组织结构分析，并用X一射线光电子能谱仪（XPS）对试样表层的Zn的电子结合能进行分析，研究稀土氧化物和纳米级粉料影响氧化锌压敏阀片性能的机理，结果表明，NdZO3、CeOZ和LaZO3加入氧化锌压敏阀片中，一方面，含稀土元素的相（以原相形式独立存在的CeOZ相、LaZO3相、含Nd的新相NaZNdZSbZ（ZnZAIO12））钉扎在晶界，阻碍晶界运动;另一方面，稀土添加剂NdZO3、CeOZ和LaZO3在陶瓷烧结过程中使ZnO晶体的自由电子浓度增大，填隙锌离子Zni的总浓度下降，因而填隙锌离子的传质能力下降，抑制了ZnO晶粒的生长。因此，NdZO3、CeOZ和LaZO3加入到氧化锌压敏阀片中，使ZnO晶粒尺寸减小，并使晶粒分布更为均匀，从而改善了压敏阀片的综合电性能。加入的稀土量存在一个最佳值，若加入量过多，将导致稀土元素在晶界富Bi相和富Sb相中的富集，造成晶界高阻层势垒电阻值的降低，非线性特性劣化。 对添加纳米氧化锌的试样进行显微组织结构分析，结果表明压敏阀片中加入纳米氧化锌后，使ZnO晶粒尺寸减小，其原因是:在烧结过程中，包裹在亚微米ZnO颗粒上的纳米ZnO粒子，降低了亚微米颗粒的表面活性，使亚微米ZnO颗粒之间的空位扩散传质减弱，阻碍了晶界迁移，使晶粒尺寸减小，从而改善了压敏阀片的综合电性能。加入的纳米氧化锌的量存在一个最佳值，若加入量过多，将导致过量的纳米氧化锌粉体中的团聚体在烧结时先行收缩，生成微气孔，而开放型的微气孔会吸附空气中的水蒸汽，造成漏电流、压比等电性能劣化。 稀土或纳米ZnO加入到压敏阀片中，对试样表层Zn的电子结合能并未四川大学博士学位论文产生明显的影响。因此，可以初步认为加入适量稀土或纳米ZnO提高压敏阀片的压敏电位梯度，其原因主要归结于减小ZnO晶粒尺寸。这一结论是根据现有的初步的试验结果得出的，关于这一问题，还有待于进一步的深入研究。 运用固体物理、半导体和电子薄膜材料的相关理论，建立数学模型，推导出了最佳掺杂含量的理论计算式，并将之推广到高温烧结的氧化锌压敏陶瓷材料，运用这一计算式定量计算NdZO3、CeOZ和LaZO3等稀土掺杂的最佳含量，计算结果与本文的实验结果比较符合。 应用日ash软件，以动画的形式模拟氧化锌压敏阀片的导电过程，较为直观地展示氧化锌压敏阀片导电的双肖特基势垒模型，这对于我们深入理解氧化锌压敏阀片的导电机理，进一步提高氧化锌压敏阀片的综合电性能，有一定的启发意义。更多还原

【Abstract】 Rare-earths oxide and nano ZnO were used as additives introducing to ZnO ceramics to improve its properties. The influence of nano ZnO on the electrical properties of varistor was studied, and the influence of Rare-earths oxide on the electrical properties of ZnO varistor was systems studied the first time.The effects of heating rate, sintering temperature, heat preserving time and cooling rate on the electrical properties of ZnO varistors was studied. The results show that it is an effective method for acquiring better electrical properties that the pressed bodies were sintered at 1150 in furnace with the temperature raised dilatorily, heat preserved for 2.5 hours and furnace cooled to room temperature.NdaO3, CeO2 and La2O3 were used as additives introduced to ZnO varistor materials. The influence of these additives on the electrical properties of ZnO varistor was studied, and the compositions of the additives were optimized. The results show that the effect of Nd2O3 on improving the varistor voltage is the most outstanding, the effect of La2O3 is more outstanding and that of CeO2 is the inferior. Adding 0.04mol% Nd2O3 improves the varistor voltage remarkably, and at the same time decreases the leakage current and the voltage ratio, then zinc oxide varistor showoutstanding comprehensively performance.Nano ZnO powder was added into varistor materials. The influence of nano ZnO on the electrical properties of varistor was studied, and the content of nano ZnO was optimized. The results show that nano ZnO improve the voltage of the varistor evidently. When the content of nano ZnO is 10wt%, the varistor voltage of ZnO varistor is higher, the voltage ratio is lower, and the leakage current is the lowest, which means better electrical properties of varistor.The microstruture of zinc oxide varistor with rare-earths oxide was studied by using scanning electronic microscope (SEM), energy spectrum apparatus (EPD), X-ray diffraction (XRD), and micrograph analysis system. It is suggested that rare-earths oxide Nd2O3> CeO2 and La2O3 reduce the grain size because the phases containing rare-earths element such as CeO2 and La2Os, which are independent phases, and the new phase Na2Nd2Sb2(Zn2AIOi2) containing neodymium all exist at the grain boundaries, hinder the movement of grain boundaries. Moreover, the additives (Nd2O3^ CeO2 and La2Oa) increase the concentration of free electron of zinc oxide crystal during sintering, then decrease the concentration of interstitial zinc, and finally hinder the growth of zinc oxide grain. Therefore, adding rare-earths oxides (Nd2Os> CeO2 and La2O3) with appropriate content decreases the size of ZnO grain evidently and makes the grain size and distribution more homogeneous, then the zinc oxide varistor show outstanding comprehensively performance.The microstruture of the varistor with nano ZnO was studied. The results show that nano additive reduces the size of ZnO grain, which leads to the evident improvement of the electrical properties of varistor.The quantitative theory of optimum doping content of electrical film materials was introduced, and an expression was obtained. Using this expression to calculate the optimum rare-earths oxides (Nd2O3, CeO2 andLa2O3) content of zinc oxide varistor, the quantitative calculation results are in accordance with the experimental results approximately.The double shottky potentical barrier was showed in form of catoon using Flash, from which we can comprehend the conduction theory of zinc oxide varistor. The electrical properties of varistor can be improved depend on it.更多还原