Volume 1, Issue 4, Pages 816-830 (December 2017) High Thermoelectric Performance of Ag9GaSe6 Enabled by Low Cutoff Frequency of Acoustic Phonons  Siqi Lin, Wen Li, Shasha Li, Xinyue Zhang, Zhiwei Chen, Yidong Xu, Yue Chen, Yanzhong Pei  Joule  Volume 1, Issue 4, Pages 816-830 (December 2017) DOI: 10.1016/j.joule.2017.09.006 Copyright © 2017 Elsevier Inc. Terms and Conditions

Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 1 Phase Characterization (A–D) Crystal structure of Ag9GaSe6 in the high temperature (>281 K) phase (A). Powder X-ray diffraction patterns (B), the lattice parameter (C), and room temperature Hall carrier concentration (D) for Ag9Ga(Se1−xTex)6, indicating formation of a solid solution. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 2 Microstructures of Ag9GaSe6 (A–D) SEM image (A) and the corresponding EDS composition mapping of Ag (B), Se (C), Ga (D) for Ag9GaSe6. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 3 Optical Absorption The normalized optical absorption versus photon energy at room temperature for Ag9Ga(Se1−xTex)6. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 4 Molecular Dynamics Simulations (A–C) Crystal structure of Ag9GaSe6 in the low-temperature phase projected onto the (100) plane (A) and the corresponding atomic trajectories at (B) 300 K and (C) 500 K, with Ag in blue, Ga in red, and Se in green. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 5 Electron Density Distribution (A and B) Electron density isosurface of 0.4 e/Å3 in Ag9GaSe6 (A) and the electron density distribution in an atomic plane crossing the Se-Ga-Se bonds (B). Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 6 Phonon Dispersion (A and B) Calculated phonon dispersions (A) and the projected phonon density of states (B) for Ag9GaSe6. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 7 Survey of ωm versus κL Room temperature lattice thermal conductivity versus the cutoff frequency of acoustic phonons for semiconductors. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 8 Thermal Properties Temperature-dependent total thermal conductivity and lattice thermal conductivity for Ag9Ga(Se1−xTex)6, compared with the lattice thermal conductivity of Ga2Se3 with intrinsic vacancies.52 Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 9 Band Structure DFT band structure of Ag9GaSe6 in P213 phase. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 10 Electronic Transport Properties (A–D) Temperature-dependent Hall mobility, μH (A), density-of-state effective mass, m* and deformation potential coefficient, Edef (B), Hall carrier concentration-dependent Seebeck coefficient (C), and Hall mobility (D) at 300, 500, and 800 K for Ag9GaSe6. The solid curves in (C) and (D) show the SPB model predictions. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 11 Thermoelectric Transport Properties (A–C) Temperature-dependent Seebeck coefficient (A), resistivity (B), and figure of merit, zT (C) for Ag9Ga(Se1−xTex)6. (D) The model-predicted zT versus carrier concentration at 300, 500, and 800 K for Ag9GaSe6. Joule 2017 1, 816-830DOI: (10.1016/j.joule.2017.09.006) Copyright © 2017 Elsevier Inc. Terms and Conditions