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首页> 外文期刊>Advanced Functional Materials >High Thermoelectric Performance in the Wide Band-Gap AgGa_(1-x)Te_2 Compounds: Directional Negative Thermal Expansion and Intrinsically Low Thermal Conductivity
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High Thermoelectric Performance in the Wide Band-Gap AgGa_(1-x)Te_2 Compounds: Directional Negative Thermal Expansion and Intrinsically Low Thermal Conductivity

机译：宽带隙AgGa_（1-x）Te_2化合物的高热电性能：方向性负热膨胀和固有的低热导率

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摘要

A deficiency of Ga in wide band-gap AgGa1-xTe2 semiconductors (1.2 eV) can be used to optimize the electrical transport properties and reduce the thermal conductivity to achieve ZT 1 at 873 K. First-principles density functional theory calculations and a Boson peak observed in the low temperature heat capacity data indicate the presence of strong coupling between optical phonons with low frequency and heat carrying acoustical phonons, resulting in a depressed maximum of Debye frequency in the first Brillouin zone and low phonon velocities. Moreover, the Ag Symbol of the Klingon Empire Te bond lengths and Te Symbol of the Klingon Empire Ag Symbol of the Klingon Empire Te bond angles increase with rising temperature, leading to a significant distortion of the [AgTe4](7-) tetrahedra, but an almost unmodified [GaTe4](5-) tetrahedra. This behavior results in lattice expansion in the ab-plane and contraction along the c-axis, corresponding to the positive and negative Gruneisen parameters in the phonon spectral calculations. This effect gives rise to the large anharmonic behavior of the lattice. These factors together with the low frequency vibrations of Ag and Te atoms in the structure lead to an ultralow thermal conductivity of 0.18 W m(-1) K-1 at 873 K.
机译：宽带隙AgGa1-xTe2半导体（1.2 eV）中Ga的不足可用于优化电传输性能并降低热导率，以在873 K时实现ZT>1。第一原理密度泛函理论计算和玻色子低温热容数据中观察到的峰值表明，低频光学声子与载热声子之间存在强耦合，导致第一个布里渊区的德拜频率最大值降低且声子速度降低。而且，克林贡帝国Te键长度的Ag符号和克林贡帝国Te符号的Ag符号随着温度的升高，克林贡帝国Te键的Ag符号增加，导致[AgTe4]（7-）四面体的明显变形，但是几乎未修饰的[GaTe4]（5-）四面体。此行为导致晶格在ab平面中膨胀并沿c轴收缩，与声子光谱计算中的正负Gruneisen参数相对应。该效应引起晶格的大非谐行为。这些因素以及结构中的Ag和Te原子的低频振动导致在873 K时具有0.18 W m（-1）K-1的超低导热率。

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