填充方钴矿热电材料器件失效机制与服役行为研究

With the development of space science and technology of our country, radioisotope thermoelectric generators (RTGs), which are of long life and high stability, are in urgent need. High performance filled skutterudite thermoelectric materials are the first choice for the next generation RTGs because they are expected to increase energy conversion efficiency, decrease the usage of precious radioisotopes and cut down the cost of RTGs considerably. Service behavior of thermoelectric materials/devices is the basis for RTGs' structural design and performance optimization. In this project service behavior and failure mechanisms of filled skutterudite materials/devices will be studied. Simulating service condition experimental method will be set up to carry out experiments, to characterize service properties and microstructures of filled skutterudite materials/devices. The effects of service conditions on the evolution of performance and microstructure of filled skutterudite materials/devices will be revealed and failure mechanisms of the devices will be investigated. All these will provide theoretical basis for the design, integration and coating of high performance filled skutterudite devices. A failure model of filled skutterudite devices will be set up to predict the properties and life of RTGs based on filled skutterudite materials/devices. This study will also provide data for the application of the high performance thermoelectric devices in RTGs and optimum design and integration of RTGs.

我国空间技术的发展迫切需要同位素温差电池这种长寿命高可靠的电源。高性能填充方钴矿热电材料有望显著提高同位素温差电池的热电转换效率，节省昂贵的同位素热源，降低成本，是下一代同位素温差电池首选的热电材料。热电发电材料器件的服役行为是温差电池结构设计与综合性能优化的技术基础。本项目开展填充方钴矿热电材料器件失效机制及服役行为研究，建立填充方钴矿热电器件模拟服役环境实验方法，对填充方钴矿热电材料器件的服役性能和微观结构进行表征，揭示服役条件对填充方钴矿热电材料器件性能和微观结构演变的影响规律，阐述填充方钴矿热电器件的失效机制，为高效热电发电器件的优化设计与集成封装奠定理论基础；建立填充方钴矿热电器件的失效模型，结合模拟仿真计算，预测以填充方钴矿器件为热电转换部件的同位素温差电池的性能和寿命，为高效填充方钴矿热电器件在同位素温差电池中应用和同位素温差电池的优化设计与集成技术的开发提供科学依据。

同位素温差电池（RTG）作为空间和特殊军用电源在空间探测和国家安全方面获得了重要的应用。高性能填充方钴矿热电材料有望显著提高RTG的热电转换效率，是下一代RTG首选的热电材料。研究认识填充方钴矿热电材料器件的服役行为和失效机制，对高性能填充方钴矿热电器件的优化设计及其在同位素温差电池中应用具有重要意义。本项目开展了高性能填充方钴矿器件技术——大尺寸块体材料、电极及封装涂层制备等技术研究，研制了高性能填充方钴矿热电发电器件；开展了热电发电器件模拟环境实验系统设计集成研究，建立了填充方钴矿热电器件在温差发电器（TEG）中工作的模拟环境实验方法，并开展了填充方钴矿热电发电器件模拟月球环境服役的实验研究。结果显示，当填充方钴矿器件高温端在较低温度（~525℃）保持时，TEG输出基本稳定；当填充方钴矿器件高温端在较高温度（~600℃）保持时，TEG输出波动大且发生衰减；当模拟月夜时，TEG的输出因温差增大不降反升，且基本稳定；当模拟月昼时，TEG的输出因温差减小而下降，一段时间后，TEG输出发生不可逆转的大幅度下降。对填充方钴矿热电发电器件性能蜕变、失效的原因及其机制进行了研究探讨，填充方钴矿材料低熔点组元Sb的遗失、器件界面扩散、裂纹及封装涂层因方钴矿材料臌胀脱落是器件性能加速蜕变的原因，而采用锡焊连接低温端电极是填充方钴矿器件在模拟月昼时发生快速失效的根本原因，其失效机制是器件结构应力与器件低温端电极界面结合力大幅下降共同作用的结果。本项目的研究结果对月球环境应用的高性能填充方钴矿热电发电器件和RTG的优化设计具有参考价值。