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Remarkable Thermoelectric Performance in K2CdPb Crystals with 1D Building Blocks via Structure Particularity and Bond Heterogeneity

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journal contribution
posted on 2022-04-12, 08:43 authored by Jie Zhang, Dan He, Hailong Jiang, Xiaohong Xia, Yun Gao, Zhongbing Huang
Identifying approaches that reduce thermal conductivity with little impact on electrical transport performance remains a central challenge for the thermoelectric community. Here, we use density functional theory calculations to demonstrate that K2CdX (XSn, Pb), with a crystal structure composed of a one-dimensional zigzag Cd-X chain sublattice and an isolated alkali metal K atom, exhibits favorable electronic and phonon transport as well as superior thermoelectric conversion efficiency. We reveal that the presence of a long-range ionic bond and multiple band characteristics lead to “electron crystal”-like electrical transport performance. On the other hand, the ultralow lattice thermal conductivity (κL) of the K2CdX compound mainly originates from the strong structural anharmonicity, which is caused by a low-dimensional sublattice combined with the heterogeneity of a weak chemical bond and the rattling vibration of K atoms in a crystal matrix. As a result, high average carrier mobility (>20 cm2 V–1 S–1), low lattice thermal conductivity below 0.4 W/mK, and spectacularly high average zT larger than 2.0 predicted for the K2CdPb system highlight the direction for identifying compounds with potential thermoelectric performance in this crystal family.