多组元共掺杂TiO2陶瓷晶界偏析及晶界势垒结构研究

TiO2 varistor ceramics is a kind of polycrystalline ceramic materials with typical grain boundary electrical properties, and the electrical properties are closely related to the grain boundary structure and grain boundary barriers structure. Combining with experiments and theoretical calculations to study the main factors influencing grain boundary segregation, and then providing the experimental and theoretical basis to control the grain boundary segregation and grain boundary barriers structure. Firstly, grain boundary segregation and grain boundaries potential barriers of TiO2 varistor ceramics will be theoretically predicted by using the empirical model and the first principles respectively. Secondly, the impact of doping and process parameters on grain boundary segregation and grain boundaries potential barriers will be investigated by experiments. Thirdly, through the experimental process parameters, structure testing and performance testing，we can get the main parameters of grain boundary segregation and grain boundary barrier structure, and comparing with the experimental data and the theoretical calculation, to improve theory method and perfect theoretical calculation. Finally, according to the improved theoretical calculation and experiments to show the influence of grain boundary segregation on grain boundary barriers structure. The effective control of the grain boundary segregation and the rational design of grain boundary barriers structure will provide the theoretical support to electronic components which based on the grain boundary barriers and the development of new electronic components.

TiO2压敏陶瓷是一种具有典型晶界电学性质的多晶陶瓷材料，材料的电学性质与晶界结构和晶界的势垒结构密切相关。将实验研究和理论计算相结合，研究影响晶界偏析的主要因素，为晶界偏析控制和晶界势垒结构控制提供实验和理论依据。.第一，分别采用经验模型和第一性原理对TiO2 压敏陶瓷的晶界偏析和晶界势垒的一般性质进行理论预测。第二，采用实验方法研究共掺杂、工艺参数对晶界偏析和晶界势垒的影响。第三，通过实验工艺参数、结构检测和性能测试得到晶界偏析和晶界势垒结构的主要参数，对比实验数据与理论计算，改进理论计算方法完善理论计算。最后，根据修正完善的理论计算，用实验验证晶界偏析对晶界势垒结构的影响。.晶界偏析的有效控制和晶界势垒结构的合理设计将为基于晶界势垒的电子元器件及开发新型电子元器件提供理论支持。

选用Nb2O5、Ta2O5和V2O5作施主掺杂剂，CaCO3、BaCO3、SrCO3和Y2O3作受主掺杂剂，通过不添加或添加Ge或GeO2以及同时添加Ge和GeO2，采用传统的球磨-成型-烧结陶瓷生产工艺制备TiO2基压敏陶瓷样品，使用XRD分析物相、SEM观察微观结构、EDAX分析元素含量、XPS分析元素化合价和TEM观察晶界结构等现代材料分析与测试技术，详细研究了Ge和GeO2单掺杂和共掺杂对不同施主和受主掺杂TiO2压敏陶瓷的微观结构和压敏性能影响，得到如下结论：. (1) 添加Ge和GeO2，由于Ge和GeO2具有较低熔点，烧结过程中出现液相，为受主离子充分偏析在晶界提供有利条件，增加界面受主态密度NS和晶界势垒高度ΦB，因此提高非线性系数α值；.(2) 添加Ge和GeO2，烧结过程中生成GeO，Ge2+由于半径较大偏析在晶界，进一步增加NS和ΦB，进一步提高α值；.(3) GeO2 是优良半导体，GeO2溶进TiO2晶格提高了晶粒的半导化程度，因此减小EB。.(4) GeO2促进晶粒生长，减小晶界宽度有助于减小势垒宽度XD，同时减少沿样品厚度方向的晶界数量 ，从而进一步提高α 值和减小压敏电压EB。