Condensed point defects enhance thermoelectric performance of rare-earth Lu-doped GeTe. (10th July 2023)

• Record Type: Journal Article
• Authors: Lyu, Wan-Yu; Liu, Wei-Di; Li, Meng; Shi, Xiao-Lei; Hong, Min; Cao, Tianyi; Guo, Kai; Luo, Jun; Zou, Jin; Chen, Zhi-Gang
• Is Part Of: Journal of materials science & technology. Volume 151(2023)
• Page Start: 227
• Page End: 233
• Publication Date: 2023-07-10
• Subjects: Thermoelectric -- Rare-earth -- Thermal conductivity -- Carrier concentration; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2023.01.004
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Lu reduces lattice thermal conductivity by condensed point defect scattering. Sb co-doping optimizes the carrier concentration to 1.77 × 10 20 cm −3 . Enhanced figure of merit 1.75 was obtained of Ge0.9 Lu0.02 Sb0.08 Te at 673 K. Abstract: Heavy rare-earth element doping can effectively strengthen phonon scattering, suppress the lattice thermal conductivity, and enhance the overall thermoelectric performance of GeTe. However, the large electronegativity difference between rare-earth elements (such as La, Eu, and Gd) and Ge refrains the doping limit of rare-earth elements below 1 mol.% in GeTe. Here, compared with other rare earth elements, Lu was found to have a relatively small radius and electronegativity difference with Ge, which can induce a high doping level in GeTe. The result shows that Lu doping effectively reduces the lattice thermal conductivity from 0.77 W m −1 K −1 of GeTe to 0.35 W m −1 K −1 of Ge0.98 Lu0.02 Te at 673 K, and further induces a high zT value of 1.5 in Ge0.98 Lu0.02 Te at 673 K. Extra Sb alloying optimizes the carrier concentration from 1.02 × 10 21 cm −3 of Ge0.98 Lu0.02 Te to 1.77 × 10 20 cm −3 of Ge0.90 Lu0.02 Sb0.08 Te, which results in a reasonable power factor of 33.82 µW cm −1 K −2 and a low electrical thermal conductivity of 0.75 W m −1 K −1 at 673 K in Ge0.90 Lu0.02 Sb0.08 Te. Correspondingly, a peak zT of 1.75 at 673 K and an average zT of 0.92 within the temperature range of 303–723 K are obtained in Ge0.9 Lu0.02 Sb0.08 Te. This study indicates that Lu and Sb co-doping can effectively boost the thermoelectric performance of GeTe-based thermoelectric materials.