Effects of aluminum content on thermoelectric performance of AlxCoCrFeNi high-entropy alloys

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

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.

Original languageEnglish
Article number160811
JournalJournal of Alloys and Compounds
Volume883
DOIs
Publication statusPublished - 25 Nov 2021
Externally publishedYes

Keywords

  • First-principles calculations
  • High-entropy alloy
  • Mass mismatch effects
  • Molecular dynamics
  • Thermoelectric property

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