Band engineering and improved thermoelectric performance in p-type SmMg2Sb2: A first-principles study. (October 2022)

• Record Type: Journal Article
• Authors: Yuan, M.H.; Wang, R.Y.; Yang, H.L.; Le, W.K.; Yang, W.W.; Lv, J.Y.; Liu, R.T.; Liu, S.H.; Zhang, Q.; Li, X.G.; Tan, X.J.; Shuai, J.
• Is Part Of: Materials today physics. Volume 27(2022)
• Publication Date: 2022-10
• Subjects: Phonon softening -- Band convergence -- SmMg2Sb2 -- Crystal field effect -- Zintl thermoelectric; Materials science -- Periodicals; Physics -- Periodicals; Electronic journals; 530.41
• DOI: 10.1016/j.mtphys.2022.100779
• Languages: English
• ISSNs: 2542-5293

Abstract

Abstract: The thermoelectric properties of p -type SmMg2 Sb2 are investigated by using the density functional theory and the Boltzmann transport equation method. It is found that SmMg2 Sb2 shows a narrow band gap characteristic, and the crystal field splitting and spin-orbital coupling effect result in a singly degenerate valence band maximum. Meanwhile, SmMg2 Sb2 exhibits an intrinsic low lattice thermal conductivity owing to the obvious phonon softening in the low-frequency acoustic branches. Based on a careful analysis of the band structure, we propose a scheme of metallic dopant at Sm site to promote the valence band convergence and improve the Seebeck coefficient. The improved thermoelectric properties are numerically confirmed in the Ba-doped p -type SmMg2 Sb2, where a significantly improved ZT of 1.6 at 750 K is predicted with the synergistical effects of band engineering and enhanced phonon scattering. Graphical abstract: Image 1 Highlights: The single VBM in SmMg2 Sb2 results from the spin-orbital coupling and crystal field splitting. SmMg2 Sb2 exhibits an intrinsic low κ l owing to the obvious phonon softening. Substitution of Sm by a more metallic dopant could screen the crystal field effect and promote valence band convergence. An improved ZT of 1.6 is predicted in Ba-doped p -type SmMg2 Sb2 .