Liao Kunyen, Shibata Kiyou, Mizoguchi Teruyasu
Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan.
Nano Lett. 2021 Dec 22;21(24):10416-10422. doi: 10.1021/acs.nanolett.1c03735. Epub 2021 Dec 2.
The presence of grain boundaries (GBs) has a great impact on the coefficient of thermal expansion (CTE) of polycrystals. However, direct measurement of local expansion of GBs remains challenging for conventional methods due to the lack of spatial resolution. In this work, we utilized the valence electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) to directly measure the CTE of Σ5 and 45°GBs of SrTiO at a temperature range between 373 and 973 K. A CTE that was about 3 times larger was observed in Σ5 GB along the direction normal to GB plane, while only a 1.4 time enhancement was found in the 45° GB. Our result provides direct evidence that GBs contribute to the enhancement of CTE in polycrystals. Also, this work has revealed how thermodynamic properties are varied in different GB structures and demonstrated the potential of EELS for probing local thermal properties with nanometer-scale resolution.
晶界（GBs）的存在对多晶体的热膨胀系数（CTE）有很大影响。然而，由于缺乏空间分辨率，传统方法直接测量晶界的局部膨胀仍然具有挑战性。在这项工作中，我们利用扫描透射电子显微镜（STEM）中的价电子能量损失谱（EELS）在373至973 K的温度范围内直接测量SrTiO的Σ5和45°晶界的CTE。在垂直于晶界平面的方向上，Σ5晶界的CTE大约大3倍，而在45°晶界中仅发现1.4倍的增强。我们的结果提供了直接证据，证明晶界有助于增强多晶体的CTE。此外，这项工作揭示了不同晶界结构中热力学性质是如何变化的，并展示了EELS在以纳米级分辨率探测局部热性质方面的潜力。
