School of Materials Science and Engineering, Beihang University , Beijing 100191, China.
Department of Physics, South University of Science and Technology of China , Shenzhen 518055, China.
J Am Chem Soc. 2016 Dec 21;138(50):16364-16371. doi: 10.1021/jacs.6b09568. Epub 2016 Dec 12.
We report that KBiSe exhibits multiple conduction bands that lie close in energy and can be activated through doping, leading to a highly enhanced Seebeck coefficient and a high power factor with elevated temperature. Meanwhile, the large unit cell, complex low symmetry crystal structure, and nondirectional bonding lead to the very low lattice thermal conductivity of KBiSe, ranging between 0.42 and 0.20 W m K in the temperature interval 300-873 K. Experimentally, we further support the low thermal conductivity of KBiSe using phonon velocity measurements; the results show a low average phonon velocity (1605 ms), small Young's modulus (37.1 GPa), large Grüneisen parameter (1.71), and low Debye temperature (154 K). A detailed investigation of the microstructure and defects was carried out using electron diffraction and transmission microscopy which reveal the presence of a KBiSe minor phase intergrown along the side of the KBiSe phase. The combination of enhanced power factor and low thermal conductivity results in a high ZT value of ∼1.3 at 873 K in electron doped KBiSe material.
我们报告说，KBiSe 具有多个能量相近的导带，可以通过掺杂来激活，从而在高温下显著提高 Seebeck 系数和功率因数。同时，大的单位晶胞、复杂的低对称晶体结构和非定向键导致 KBiSe 的晶格热导率非常低，在 300-873 K 的温度范围内，晶格热导率在 0.42 到 0.20 W m K 之间。实验上，我们使用声子速度测量进一步支持了 KBiSe 的低热导率；结果表明平均声子速度较低（1605 ms）、杨氏模量较小（37.1 GPa）、Grüneisen 参数较大（1.71）和德拜温度较低（154 K）。通过电子衍射和透射显微镜对微观结构和缺陷进行了详细研究，结果表明在 KBiSe 相的侧面存在 KBiSe 次要相的共生。在电子掺杂的 KBiSe 材料中，高功率因数和低热导率的结合导致在 873 K 时 ZT 值约为 1.3。
