Tian Jing, Ma Weiliang, Boulet Pascal, Record Marie-Christine
MADIREL, Department of Chemistry, CNRS, Aix-Marseille University, 13013 Marseille, France.
IM2NP, Department of Chemistry, CNRS, Aix-Marseille University, 13013 Marseille, France.
Materials (Basel). 2023 Jul 15;16(14):5015. doi: 10.3390/ma16145015.
In recent years, layered chalcogenides have attracted interest for their appealing thermoelectric properties. We investigated the GeSbTe compound in two different stacking sequences, named stacking 1 (S1) and stacking 2 (S2), wherein the Ge and Sb atomic positions can be interchanged in the structure. The compound unit cell, comprising nine atoms, is made of two layers separated by a gap. We show, using the quantum theory of atoms in molecules, that the bonding across the layers has characteristics of transit region bonding, though with a close resemblance to closed-shell bonding. Both S1 and S2 are shown to bear a similar small gap. The full determination of their thermoelectric properties, including the Seebeck coefficient, electrical conductivity and electronic and lattice thermal conductivities, was carried out by solving the Boltzmann transport equation. We show that stacking 1 exhibits a larger Seebeck coefficient and smaller electrical conductivity than stacking 2, which is related to their small electronic gap difference, and that S1 is more suitable for thermoelectric application than S2. Moreover, under certain conditions of temperature and doping level, it could be possible to use S1-GeSbTe as both a and leg in a thermoelectric converter. Under biaxial, tensile and compressive strains, we observe that the thermoelectric properties are improved for both S1 and S2. Furthermore, the increase in the power factor of S1 in the cross-plane direction, namely perpendicular to the gap between the layers, shows that strains can counteract the electronic transport hindrance due to the gap.
近年来，层状硫属化物因其吸引人的热电性能而备受关注。我们研究了具有两种不同堆叠顺序的GeSbTe化合物，分别命名为堆叠1（S1）和堆叠2（S2），其中Ge和Sb的原子位置在结构中可以互换。该化合物的晶胞由九个原子组成，由两层通过一个间隙隔开。我们使用分子中原子的量子理论表明，层间键合具有过渡区键合的特征，尽管与闭壳层键合非常相似。结果表明，S1和S2都具有相似的小间隙。通过求解玻尔兹曼输运方程，对它们的热电性能进行了全面测定，包括塞贝克系数、电导率以及电子和晶格热导率。我们发现，堆叠1比堆叠2表现出更大的塞贝克系数和更小的电导率，这与它们较小的电子能隙差异有关，并且S1比S2更适合热电应用。此外，在一定的温度和掺杂水平条件下，有可能将S1-GeSbTe用作热电转换器中的a腿和b腿。在双轴、拉伸和压缩应变下，我们观察到S1和S2的热电性能都得到了改善。此外，S1在垂直于层间间隙方向（即跨平面方向）的功率因数增加，表明应变可以抵消由于间隙导致的电子输运阻碍。
