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Effects of aluminum content on thermoelectric performance of Al CoCrFeNi high-entropy alloys

Published

Author(s)

Md Abdullah Al Hasan, Jiaqi Wang, Seungha Shin, Dustin A. Gilbert, Peter K. Liaw, Nan Tang, W. L. N. C. Liyanage, Louis Santodonato, Lisa Debeer-Schmitt, Nicholas Butch

Abstract

Introducing a non-regular distribution in the mass and bonding by including distinctly different elements can reduce the phonon transport even within structurally well-ordered materials. These distributions are a quality of all high-entropy alloys (HEAs), however the inclusion of aluminum in AlxCoCrFeNi is particularly impactful due to the large mismatch in atomic mass with other components. The resultant low phonon conductivity is a requirement for high thermoelectric performance, motivating the investigation of the effects of Al content on phonon transport as well as other thermoelectric properties. This work examines the phonon and electron transport and thermoelectric conversion properties with various Al contents (0 ≤ xAl ≤ 2) in this Cantor alloy using first-principles calculations, molecular dynamics, and semi-classical Boltzmann transport theory. The calculated phonon density of states and thermoelectric properties present reasonable agreements with experiments, including neutron scattering. A large reduction of phonon conductivity (kL) is observed even with low xAls, which we attribute to effective phonon scatterings by the large mass mismatch. However, its temperature dependence is not significant, demonstrating a minor contribution of interphonon scattering. In contrast, electrical conductivity (σ) and Seebeck coefficient (S) increase with temperature at higher xAls with body-centered cubic structures. Therefore, the thermoelectric figure of merit (ZT) of AlxCoCrFeNi HEAs is enhanced by increasing the Al content mainly due to the increase of the thermoelectric power factor (σS2) at high temperatures, while at low temperatures the phonon-scattering enhancement by mass mismatch is also important.
Citation
Journal of Alloys and Compounds
Volume
883

Keywords

phonon, high entropy alloy

Citation

Al Hasan, M. , Wang, J. , Shin, S. , Gilbert, D. , Liaw, P. , Tang, N. , Liyanage, W. , Santodonato, L. , Debeer-Schmitt, L. and Butch, N. (2021), Effects of aluminum content on thermoelectric performance of Al CoCrFeNi high-entropy alloys, Journal of Alloys and Compounds, [online], https://doi.org/10.1016/j.jallcom.2021.160811 (Accessed April 19, 2024)
Created June 15, 2021, Updated March 25, 2024