ABSTRACT The quest to improve the thermoelectric figure of merit has mainly followed the roadmap of lowering the thermal conductivity while keeping unaltered the power factor of the material. Ideally an electron-crystal phonon-glass system is desired. In this work, we report an extraordinary reduction of the cross-plane thermal conductivity in crystalline (TiNiSn):(HfNiSn) half-Heusler superlattices (SLs). We create SLs with thermal conductivities below the effective amorphous limit, which is kept in a large temperature range (120–300 K). We measured thermal conductivity at room temperature values as low as 0.75 W m−1 K−1, the lowest thermal conductivity value reported so far for half-Heusler compounds. By changing the deposition conditions, we also demonstrate that the thermal conductivity is highly impacted by the way the single segments of the SL grow. These findings show a huge potential for thermoelectric generators where an extraordinary reduction of the thermal conductivity is required but without losing the crystal quality of the system

中文翻译：

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结晶半赫斯勒超晶格的亚非晶热导率

摘要 改善热电品质因数的探索主要遵循降低热导率同时保持材料功率因数不变的路线图。理想情况下，需要电子晶体声子玻璃系统。在这项工作中，我们报告了晶体 (TiNiSn):(HfNiSn) 半赫斯勒超晶格 (SL) 中跨平面热导率的显着降低。我们创建了热导率低于有效非晶极限的 SL，该极限保持在较大的温度范围内（120-300 K）。我们在室温下测量了低至 0.75 W m-1 K-1 的热导率值，这是迄今为止报道的半赫斯勒化合物的最低热导率值。通过改变沉积条件，我们还证明了热导率受到 SL 单段生长方式的高度影响。这些发现显示了热电发电机的巨大潜力，其中需要显着降低热导率但不损失系统的晶体质量