High‐Performance Thermoelectric α‐Ag9Ga1−xTe6 Compounds with Ultralow Lattice Thermal Conductivity Originating from Ag9Te2 Motifs. (27th July 2022)

• Record Type: Journal Article
• Authors: Tang, Yingfei; Yu, Yimeng; Zhao, Na; Liu, Keke; Chen, Haijie; Stoumpos, Constantinos C.; Shi, Yixuan; Chen, Shuo; Yu, Lingxiao; Wu, Jinsong; Zhang, Qingjie; Su, Xianli; Tang, Xinfeng
• Is Part Of: Angewandte Chemie. Volume 134:Number 36(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-07-27
• Subjects: α-Ag9GaTe6 -- Crystal Structure -- Ga Deficiency -- Thermoelectrics -- Ultralow Lattice Thermal Conductivity; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202208281
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: We have determined the complex atomic structure of high‐temperature α‐Ag9 GaTe6 phase with a hexagonal lattice ( P 63 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 Ga1− x Te6 compounds effectively optimizes the electronic transport properties. Ag9 Ga0.91 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 Ga0.95 Te6, which is 41 % higher than that of the pristine Ag9 GaTe6 sample. Abstract : The high‐temperature crystal structure of α‐Ag9 GaTe6 shows a hexagonal structure. Highly disordered Ag atoms vibrate in‐harmonically leading to an intrinsically ultralow lattice thermal conductivity. Meanwhile, the deficiency of Ga in Ag9 Ga1− x Te6 compounds effectively optimizes the electronic transport properties. All these factors contribute to an improved thermoelectric Figure of Merit ZT value of 1.13 at 623 K for Ag9 Ga0.95 Te6 .