High-Performance Thermoelectric α-Ag9 Ga1-x Te6 Compounds with Ultralow Lattice Thermal Conductivity Originating from Ag9 Te2 Motifs

Yingfei Tang; Yimeng Yu; Na Zhao; Keke Liu; Haijie Chen; Constantinos C Stoumpos; Yixuan Shi; Shuo Chen; Lingxiao Yu; Jinsong Wu; Qingjie Zhang; Xianli Su; Xinfeng Tang

doi:10.1002/anie.202208281

High-Performance Thermoelectric α-Ag₉ Ga_1-x Te₆ Compounds with Ultralow Lattice Thermal Conductivity Originating from Ag₉ Te₂ Motifs

Angew Chem Int Ed Engl. 2022 Sep 5;61(36):e202208281. doi: 10.1002/anie.202208281. Epub 2022 Jul 27.

Authors

Yingfei Tang^{1

2}, Yimeng Yu^{1

3}, Na Zhao¹, Keke Liu¹, Haijie Chen⁴, Constantinos C Stoumpos⁵, Yixuan Shi^{1

2}, Shuo Chen¹, Lingxiao Yu^{1

2}, Jinsong Wu^{1

3}, Qingjie Zhang¹, Xianli Su¹, Xinfeng Tang¹

Affiliations

¹ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.
² International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, China.
³ Nanostructure Research Center, Wuhan University of Technology, Wuhan, 430070, China.
⁴ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Institute of Functional Materials, College of Materials Science and Engineering, Donghua University, Shanghai, 201620, China.
⁵ Department of Materials Science and Technology, Voutes Campus, University of Crete, Iraklio, Heraklion, 70013, Greece.

PMID: 35821569
DOI: 10.1002/anie.202208281

Abstract

We have determined the complex atomic structure of high-temperature α-Ag₉ GaTe₆ phase with a hexagonal lattice (P6₃ mc space group, a=b=8.2766 Å, c=13.4349 Å). The structure has outer [GaTe₄ ]^5- tetrahedrons and inner [Ag₉ Te₂ ]⁵⁺ clusters. All of the Ag ions are disorderly distributed in the lattice. Seven types of the Ag atoms constitute the cage-like [Ag₉ Te₂ ]⁵⁺ clusters. The highly disordered Ag ions vibrate in-harmonically, producing strong coupling between low frequency optical phonons and acoustic phonons. This in conjunction with a low sound velocity of 1354 m s^-1 leads to an ultralow thermal conductivity of 0.20 W m^-1 K^-1 at 673 K. Meanwhile, the deficiency of Ga in Ag₉ Ga_1-x Te₆ compounds effectively optimizes the electronic transport properties. Ag₉ Ga_0.91 Te₆ attains a highest power factor of 0.40 mW m^-1 K^-2 at 673 K. All these contribute to a much-improved ZT value of 1.13 at 623 K for Ag₉ Ga_0.95 Te₆ , which is 41 % higher than that of the pristine Ag₉ GaTe₆ sample.

Keywords: Crystal Structure; Ga Deficiency; Thermoelectrics; Ultralow Lattice Thermal Conductivity; α-Ag9GaTe6.

Abstract

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