Thermal transport is a key performance metric for thorium dioxide in many applications where defect-generating radiation fields are present. An understanding of the effect of nanoscale lattice defects on thermal transport in this material is currently unavailable due to the lack of a single crystal material from which unit processes may be investigated. In this work, a series of high-quality thorium dioxide single crystals are exposed to 2 MeV proton irradiation at room temperature and 600 °C to create microscale regions with varying densities and types of point and extended defects. Defected regions are investigated using spatial domain thermoreflectance to quantify the change in thermal conductivity as a function of ion fluence as well as transmission electron microscopy and Raman spectroscopy to interrogate the structure of the generated defects. Together, this combination of methods provides important initial insight into defect formation, recombination, and clustering in thorium dioxide and the effect of those defects on thermal transport. These methods also provide a promising pathway for the quantification of the smallest-scale defects that cannot be captured using traditional microscopy techniques and play an outsized role in degrading thermal performance.

中文翻译：

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晶格缺陷、复合和聚集对单晶二氧化钍热传输的影响

在许多存在缺陷产生辐射场的应用中，热传输是二氧化钍的关键性能指标。由于缺乏可以研究单元过程的单晶材料，因此目前无法了解纳米级晶格缺陷对这种材料中热传输的影响。在这项工作中，一系列高质量的二氧化钍单晶在室温和 600°C 下暴露于 2 MeV 质子辐射，以创建具有不同密度和类型的点和扩展缺陷的微尺度区域。缺陷区域的研究使用空间域热反射来量化作为离子注量函数的热导率变化，以及透射电子显微镜和拉曼光谱以询问所产生缺陷的结构。总之，这种方法的组合为二氧化钍中的缺陷形成、重组和聚集以及这些缺陷对热传输的影响提供了重要的初步见解。这些方法还为量化使用传统显微镜技术无法捕获的最小尺度缺陷提供了有希望的途径，这些缺陷在降低热性能方面发挥了巨大的作用。二氧化钍中的聚集以及这些缺陷对热传输的影响。这些方法还为量化使用传统显微镜技术无法捕获的最小尺度缺陷提供了有希望的途径，这些缺陷在降低热性能方面发挥了巨大的作用。二氧化钍中的聚集以及这些缺陷对热传输的影响。这些方法还为量化使用传统显微镜技术无法捕获的最小尺度缺陷提供了有希望的途径，这些缺陷在降低热性能方面发挥了巨大的作用。