Soft Phonon Modes Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance in AgCuTe,Angewandte Chemie International Edition

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Soft Phonon Modes Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance in AgCuTe
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2018-03-12 , DOI: 10.1002/anie.201801491
Subhajit Roychowdhury ₁ , Manoj K. Jana ₁ , Jaysree Pan ₁ , Satya N. Guin ₁ , Dirtha Sanyal ₂ , Umesh V. Waghmare ₁ , Kanishka Biswas ₁

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Crystalline solids with intrinsically low lattice thermal conductivity (κ_L) are crucial to realizing high‐performance thermoelectric (TE) materials. Herein, we show an ultralow κ_L of 0.35 Wm⁻¹ K⁻¹ in AgCuTe, which has a remarkable TE figure‐of‐merit, zT of 1.6 at 670 K when alloyed with 10 mol % Se. First‐principles DFT calculation reveals several soft phonon modes in its room‐temperature hexagonal phase, which are also evident from low‐temperature heat‐capacity measurement. These phonon modes, dominated by Ag vibrations, soften further with temperature giving a dynamic cation disorder and driving the superionic transition. Intrinsic factors cause an ultralow κ_L in the room‐temperature hexagonal phase, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high‐temperature rocksalt phase. Despite the cation disorder at elevated temperatures, the crystalline conduits of the rigid anion sublattice give a high power factor.

中文翻译：

AgCuTe中的软声子模式导致超低热导率和高热电性能

与固有的低晶格热导率（κ结晶固体_大号）是实现高性能的热电（TE）的材料是至关重要的。此，我们表明超低κ_大号0.35了Wm的^-1 ķ ^-1在AgCuTe，当与10摩尔％的Se合金，其具有1.6在670 K A显着的TE，图-的-性能指数ZT。第一性原理DFT计算揭示了室温六方相中的几种软声子模式，这在低温热容量测量中也很明显。这些受Ag振动支配的声子模式随着温度进一步软化，产生动态阳离子紊乱并驱动超离子跃迁。内在因素引起的超低κ_大号在室温六方相中，Ag / Cu阳离子的动态无序导致高温岩盐相中的声子频率降低和平均自由程。尽管在高温下阳离子紊乱，但刚性阴离子亚晶格的晶体导管仍具有较高的功率因数。

更新日期：2018-03-12

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