Liu Yukun, Xie Hongyao, Li Zhi, Zhang Yinying, Malliakas Christos D, Al Malki Muath, Ribet Stephanie, Hao Shiqiang, Pham Thang, Wang Yuankang, Hu Xiaobing, Dos Reis Roberto, Snyder G Jeffrey, Uher Ctirad, Wolverton Christopher, Kanatzidis Mercouri G, Dravid Vinayak P
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2023 Apr 7. doi: 10.1021/jacs.3c01693.
Entropy-engineered materials are garnering considerable attention owing to their excellent mechanical and transport properties, such as their high thermoelectric performance. However, understanding the effect of entropy on thermoelectrics remains a challenge. In this study, we used the PbGeSnCdTe family as a model system to systematically investigate the impact of entropy engineering on its crystal structure, microstructure evolution, and transport behavior. We observed that PbGeSnTe crystallizes in a rhombohedral structure at room temperature with complex domain structures and transforms into a high-temperature cubic structure at ∼373 K. By alloying CdTe with PbGeSnTe, the increased configurational entropy lowers the phase-transition temperature and stabilizes PbGeSnCdTe in the cubic structure at room temperature, and the domain structures vanish accordingly. The high-entropy effect results in increased atomic disorder and consequently a low lattice thermal conductivity of 0.76 W m K in the material owing to enhanced phonon scattering. Notably, the increased crystal symmetry is conducive to band convergence, which results in a high-power factor of 22.4 μW cm K. As a collective consequence of these factors, a maximum of 1.63 at 875 K and an average of 1.02 in the temperature range of 300-875 K were obtained for PbGeSnCdTe. This study highlights that the high-entropy effect can induce a complex microstructure and band structure evolution in materials, which offers a new route for the search for high-performance thermoelectrics in entropy-engineered materials.
熵工程材料因其优异的力学和输运性能，如高热电性能，而备受关注。然而，理解熵对热电学的影响仍然是一个挑战。在本研究中，我们以PbGeSnCdTe族为模型体系，系统地研究了熵工程对其晶体结构、微观结构演变和输运行为的影响。我们观察到，PbGeSnTe在室温下结晶为具有复杂畴结构的菱面体结构，并在约373 K时转变为高温立方结构。通过将CdTe与PbGeSnTe合金化，增加的组态熵降低了相变温度，并使PbGeSnCdTe在室温下稳定在立方结构中，畴结构也相应消失。高熵效应导致原子无序增加，进而由于声子散射增强，材料的晶格热导率低至0.76 W m K。值得注意的是，晶体对称性的增加有利于能带收敛，从而导致22.4 μW cm K的高功率因子。这些因素共同作用的结果是，PbGeSnCdTe在875 K时的最大值为1.63，在300-875 K温度范围内的平均值为1.02。本研究强调，高熵效应可以在材料中诱导复杂的微观结构和能带结构演变，这为在熵工程材料中寻找高性能热电材料提供了一条新途径。
