Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys,ACS Applied Materials & Interfaces

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Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2022-11-30 , DOI: 10.1021/acsami.2c16595
Nagendra S Chauhan _{1,

2,

3} , Dipanwita Bhattacharjee ₄ , Tanmoy Maiti ₃ , Yury V Kolen'ko ₂ , Yuzuru Miyazaki ₁ , Amrita Bhattacharya ₄

Affiliation

Intrinsically high lattice thermal conductivity has remained a major bottleneck for achieving a high thermoelectric figure of merit (zT) in state-of-the-art ternary half-Heusler (HH) alloys. In this work, we report a stable n-type biphasic-quaternary (Ti,V)CoSb HH alloy with a low lattice thermal conductivity κ_L ≈ 2 W m^–1 K^–1 within a wide temperature range (300–873 K), which is comparable to the reported nanostructured HH alloys. A solid-state transformation driven by spinodal decomposition upon annealing is observed in Ti_0.5V_0.5CoSb HH alloy, which remarkably enhances phonon scattering, while electrical properties correlate well with the altering electronic band structure and valence electron count (VEC). A maximum zT ≈ 0.4 (±0.05) at 873 K was attained by substantial lowering of κ_L and synergistic enhancement of the power factor. We perform first-principles density functional theory calculations to investigate the structure, stability, electronic structure, and transport properties of the synthesized alloy, which rationalize the reduction in the lattice thermal conductivity to the increase in anharmonicity due to the alloying. This study upholds the new possibilities of finding biphasic-quaternary HH compositions with intrinsically reduced κ_L for prospective thermoelectric applications.

中文翻译：

双相四元 (Ti,V)CoSb 半赫斯勒合金在较宽温度范围内的低晶格热导率

本质上高晶格热导率仍然是在最先进的三元半赫斯勒 (HH) 合金中实现高热电品质因数 ( zT ) 的主要瓶颈。在这项工作中，我们报告了一种稳定的 n 型双相四元 (Ti,V)CoSb HH 合金，其在宽温度范围 (300–873 K) 内具有低晶格热导率 κ _L ≈ 2 W m ^–1 K ^–1，这与报道的纳米结构 HH 合金相当。_{在 Ti 0.5} V _0.5中观察到退火时旋节线分解驱动的固态转变CoSb HH 合金，可显着增强声子散射，而电性能与不断变化的电子能带结构和价电子数 (VEC) 密切相关。通过大幅降低 κ _L和协同提高功率因数，在 873 K 时达到最大zT ≈ 0.4 (±0.05)。我们进行了第一性原理密度泛函理论计算，以研究合成合金的结构、稳定性、电子结构和传输特性，这使晶格热导率的降低与合金化引起的非谐性增加合理化。_{本研究支持发现具有固有降低的 κ L}的双相-四元 HH 组合物的新可能性用于未来的热电应用。

更新日期：2022-11-30

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