Meledath Valiyaveettil Suneesh, Nguyen Duc-Long, Wong Deniz P, Hsing Cheng-Rong, Paradis-Fortin Laura, Qorbani Mohammad, Sabbah Amr, Chou Ta-Lei, Wu Kuei-Kuan, Rathinam Vasudevan, Wei Ching-Ming, Chen Li-Chyong, Chen Kuei-Hsien
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
Department of Physics, National Central University, Taoyuan 32001, Taiwan.
Inorg Chem. 2022 Mar 14;61(10):4442-4452. doi: 10.1021/acs.inorgchem.1c03947. Epub 2022 Mar 3.
We report the phase evolution and thermoelectric properties of a series of Co(GeTe)Sb ( = 0-0.20) compositions synthesized by mechanical alloying. Pristine ternary Co(GeTe) skutterudite crystallizes in the rhombohedral symmetry (3̅), and Sb doping induces a structural transition to the cubic phase (ideal skutterudite, 3̅). The Sb substitution increases the carrier concentration while maintaining a high thermopower even at higher doping levels owing to an increased effective mass. The exceptional electronic properties exhibited by Co(GeTe) upon doping are attributed to the carrier transport from both the primary and secondary conduction bands, as shown by theoretical calculations. The enhanced electrical conductivity and high thermopower increase the power factor by more than 20 times. Because the dominant phonon propagation modes in binary skutterudites are associated with the vibrations of pnictogen rings, twisting the latter through the isoelectronic replacement of Sb rings with GeTe ones, as done in this study, can effectively reduce the thermal conductivity. This leads to an increase in the dimensionless figure-of-merit () by a factor of 30, reaching 0.65 at 723 K for Co(GeTe)Sb.
我们报道了通过机械合金化合成的一系列Co(GeTe)Sb（x = 0 - 0.20）成分的相演变和热电性能。原始的三元Co(GeTe)方钴矿以菱面体对称性（R3̅）结晶，而Sb掺杂会诱导结构转变为立方相（理想方钴矿，Fm3̅m）。Sb替代增加了载流子浓度，同时由于有效质量增加，即使在较高掺杂水平下也能保持较高的热电势。理论计算表明，Co(GeTe)掺杂后表现出的优异电子性能归因于来自主带和次带的载流子传输。电导率的提高和高热电势使功率因子提高了20倍以上。由于二元方钴矿中的主要声子传播模式与氮族元素环的振动有关，如本研究中通过用GeTe环对等电子的Sb环进行取代来扭曲氮族元素环，可以有效降低热导率。这导致无量纲品质因数（ZT）增加了30倍，对于Co(GeTe)0.20Sb在723 K时达到0.65。
