Phonon Bridge Effect in Superlattices of Thermoelectric TiNiSn/HfNiSn With Controlled Interface Intermixing
Phonon Bridge Effect in Superlattices of Thermoelectric TiNiSn/HfNiSn With Controlled Interface Intermixing
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DOI：
10.3390/nano10061239
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发表时间：
2020-06-01
期刊：
影响因子：
5.3
通讯作者：
Jakob, Gerhard
中科院分区：
文献类型：
--
作者：
Heinz, Sven;Angel, Emigdio Chavez;Jakob, Gerhard
热电材料中热障的实现有效地提高了热电材料的功率转换效率。为此，利用和操纵材料边界来影响声子透过率。具体地说，界面混合和地形是热输运修正的一个有用但复杂的参数。本研究研究了具有原始界面和故意劣化界面的TiNiSnHfNiSn外延薄膜多层膜，即所谓的超晶格(SL)。用高分辨电子显微镜和X射线衍射仪对其结构性质进行了详细的表征。微分3欧米伽法探测它们的热电阻率。对于中等界面质量，热电阻率达到最大值，当边界层混合程度较高时，热电阻率再次下降。对于界面质量最低的界面，与原始SL相比，界面热阻降低了23%。虽然弥散散射的吸收可能解释了热输运的初始恶化，但我们提出了一种声子桥解释，解释了临界混合以外界面热阻降低的原因。在这幅图中，定义较少的边界局部降低的声学对比度起到了促进声子跃迁的中介作用。
The implementation of thermal barriers in thermoelectric materials improves their power conversion rates effectively. For this purpose, material boundaries are utilized and manipulated to affect phonon transmissivity. Specifically, interface intermixing and topography represents a useful but complex parameter for thermal transport modification. This study investigates epitaxial thin film multilayers, so called superlattices (SL), of TiNiSn/HfNiSn, both with pristine and purposefully deteriorated interfaces. High-resolution transmission electron microscopy and X-ray diffractometry are used to characterize their structural properties in detail. A differential 3 omega-method probes their thermal resistivity. The thermal resistivity reaches a maximum for an intermediate interface quality and decreases again for higher boundary layer intermixing. For boundaries with the lowest interface quality, the interface thermal resistance is reduced by 23% compared to a pristine SL. While an uptake of diffuse scattering likely explains the initial deterioration of thermal transport, we propose a phonon bridge interpretation for the lowered thermal resistivity of the interfaces beyond a critical intermixing. In this picture, the locally reduced acoustic contrast of the less defined boundary acts as a mediator that promotes phonon transition.