Ultra-low lattice thermal conductivity driven high thermoelectric figure of merit in Sb/W co-doped GeTe

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2024-11, Vol.12 (44), p.3892-395
• Main Authors: Bayikadi, Khasim Saheb, Imam, Safdar, Tee, Wei-Shen, Kavirajan, Sugumaran, Chang, Chiao-Yu, Sabbah, Amr, Fu, Fang-Yu, Liu, Ting-Ran, Chiang, Ching-Yu, Shukla, Dinesh, Wu, Chien-Ting, Chen, Li-Chyong, Chou, Mei-Yin, Chen, Kuei-Hsien, Sankar, Raman
• Format: Article
• Language: English
• Subjects: Chemical bonds; Electrical conductivity; Electrical resistivity; Electronegativity; Figure of merit; Heat conductivity; Heat transfer; Interstitials; Lattice strain; Multiple scatter; Operating temperature; Phonons; Thermal conductivity; Thermoelectric materials; Thermoelectricity
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta05332j

High thermoelectric performance is a material challenge associated mainly with the manipulation of lattice dynamics to obtain extrinsic phonon transport routes, which can make the lattice thermal conductivity ( κ lat ) intrinsically low by introducing multiple scattering mechanisms. The present study shows that the lattice-strain-induced phonon scattering resulting from microstructural distortions in GeTe-based compounds can enable ultralow lattice thermal conductivity. The unusual lattice shrinkage, W interstitials, W nanoprecipitates, and heavy elemental mass, in Ge 0.85 Sb 0.1 W 0.05 Te culminate in an ultralow lattice thermal conductivity of ∼0.2 W m −1 K −1 at 825 K. Microstructural distortions in this Sb/W co-doped GeTe are found to be primarily associated with shorter W-Te bonding owing to the anomalous effect of the higher electronegativity of the W atoms. Furthermore, the increased electrical conductivity ( σ ) resulting from the enhanced vacancy formation caused by W doping and W interstitials synergistically contributes to optimization of the thermoelectric performance ( ZT ) to ∼2.93 at 825 K. The thermoelectric efficiency ( η ) as high as ∼17% has been obtained for a single leg in this composition at an operating temperature of 825 K, with an estimated device ZT value of ∼1.38. Phonon scattering processes to κ lat of Ge 0.85 Sb 0.1 W 0.05 Te: Umklapp, boundary, point-defect, stacking faults, resonant scattering, nanoprecipitates & microstructural effects. (b) κ lat reduction (inset: ZT enhancement).