https://scholars.lib.ntu.edu.tw/handle/123456789/639157
Title: | From stoichiometric to off-stoichiometric GeTe: Phase diagram reconstruction and thermoelectric performance reassessment | Authors: | Tsai, Yi Fen Chao, Ying Chun Hsing, Cheng Rong Wang, Kuang Kuo Tung, Yung Hsiang Yang, Chun Chuen Chen, Sinn Wen Snyder, G. Jeffrey HUNG-WEI YEN Wei, Ching Ming Wei, Pai Chun Wu, Hsin Jay |
Keywords: | Defective domain boundaries | Off-stoichiometric GeTe | Theoretical density functional theory (DFT) | Thermoelectric | Issue Date: | 15-Feb-2024 | Journal Volume: | 265 | Source: | Acta Materialia | Abstract: | This study investigates the structure, microstructure, and transport properties of off-stoichiometric GeTe (off-GeTe). In a narrow range of 50–53 at% Te, both the rhombohedral a-GeTe and orthorhombic g-GeTe phases coexist. Despite their similar chemical composition, GeTe and off-GeTe alloys exhibit distinct microstructural and thermal/electronic properties. Theoretical density functional theory (DFT) calculations were employed to verify that changes in the Ge/Te ratios influence the concentration of Ge vacancies, leading to a significant alteration in transport properties despite minor variations in chemical compositions. The off-GeTe alloy, which is free of Ge precipitates, displays defective domain boundaries, showcasing a non-typical herringbone nanostructure that is unprecedented for GeTe-based materials. Notably, the phase transition temperature of off-GeTe, at 620K, differs from its peak zT temperature of 698K. Moreover, a TE device incorporating off-GeTe demonstrates superior interfacial stability and higher energy conversion efficiency compared to its stoichiometric GeTe counterpart. Consequently, off-GeTe demonstrates superior TE performance and enhanced interfacial stability compared to stoichiometric GeTe. The addition of Sb to off-GeTe further improves its potential for TE applications by lifting the single-leg conversion efficiency greater than 3%. |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/639157 | ISSN: | 13596454 | DOI: | 10.1016/j.actamat.2023.119644 |
Appears in Collections: | 材料科學與工程學系 |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.