闪烧制备聚合物转化SiOC陶瓷导电性能调控机理的研究

Polymer-derived ceramics (PDCs) are promising materials for high-temperature sensors due to their excellent properties. In order to achieve the application of PDCs in high-temperature sensor field, their electrical conductivity must be accurate regulated via microstructure adjustion. However, PDCs sintered by conventional methods always have a low density, and the microstructure of single phase cannot be controlled. Aiming to solve these problems, polymer-derived SiOC ceramic will be synthesized and flash-sintered. Their microstructures evolution will be studied by adjusting the sintering parameters of flash sintering process. The electrical conductivity of SiOC under different temperatures and pressures will be measured and the relationship between electrical conductivity and microstructures will be investigated for the sake of regulating the electrical conductivity. This project intends to address two key scientific issues: the mechanism of flash sintering for heterogeneous phases and the regulation mechanism of electrical conductivity of SiOC; and breaks through two key techniques: measurement and analysis of joule heat during flash sintering and microstructures characterization of amorphous materials. This project is innovative in research method and characterization technique. The research results will provide powerful scientific supports for the application of PDCs in high-temperature sensor field.

聚合物转化陶瓷（PDC）近年来因其卓越的性能被视为高温传感器的理想材料，而要实现PDC材料在高温传感器领域的真正应用，必须通过调控微观结构，对其导电性能做到精确控制。针对目前传统热处理方法无法实现PDC单一相结构调控及致密化烧结的问题，本课题提出以SiOC转化陶瓷为研究对象，以闪烧法为热处理手段，通过控制闪烧工艺参数，针对性调控SiOC陶瓷微观结构，探究聚合物转化陶瓷微观结构演变规律，考察外场(温度场、应力场)作用下材料的导电性能，建立导电性能-微观结构理论模型并分析机理，最终实现对材料导电性能的精确调控。本课题拟解决闪烧对异质相作用机制及SiOC陶瓷导电性能调控机理两个关键科学问题；突破闪烧过程中焦耳热测量和分析以及非晶材料微观结构表征两个关键技术；在研究手段及表征方法上具有创新性。本课题研究成果将为聚合物转化陶瓷后期在高温传感器领域的应用提供重要科学理论依据。

聚合物转化陶瓷(Polymer Derived Ceramics，PDCs)具有优异的高温稳定性、良好的力学性能和独特的半导体性能，是一种非常有潜力的高温传感器材料。然而，聚合物转化陶瓷传感器在我国的实际应用中发展缓慢，其主要瓶颈是难以实现对聚合物转化陶瓷电学性能的精确调控。针对这一问题，本研究选取分子结构最为简单的聚硅氧烷(PSO)作为研究对象，采用闪烧技术制备聚合物转化SiOC陶瓷，研究在电场电流作用下SiOC陶瓷的微结构演变和电导率变化机理，建立SiOC陶瓷微结构和电学性能间的联系，以期实现对SiOC陶瓷电学性能的精确调控。.研究结果显示，闪烧炉温的增加能够促进PDC中的碳相由sp3向sp2的转变和碳簇的长大，碳相转变激活能约为3.19eV。SiOC陶瓷的直流电导率及交流电导率随闪烧炉温的升高而增加，电导激活能约为0.18eV，较低的电导激活能主要归因于试样内电子随闪烧电流的共同迁移。SiOC陶瓷的交流电导率随频率的变化存在一个电导驰豫过程，弛豫时间远小于传统烧结试样。此外，电流密度的增加也可以促使碳相由sp3向sp2转变，碳相转变的激活能约为1.54eV。SiOC陶瓷的直流电导率及交流电导率随闪烧电流密度的升高而增加，电导激活能约为1.16eV，说明电导率并非全由碳相转变决定，还与SiOC陶瓷内碳簇的尺寸与取向有关。SiOC陶瓷的禁带宽度随电流密度的升高而减小，主要得益于结构中氢原子的减少；而带尾态宽度随电流密度的升高而减少则与SiOC陶瓷内部的碳相有序度增大相关，电子跃迁更符合带尾跃迁机制。