Unveiling the origins of low lattice thermal conductivity in 122-phase Zintl compounds. (November 2021)

• Record Type: Journal Article
• Authors: Guo, K.; Weng, T.; Jiang, Y.; Zhu, Y.; Li, H.; Yuan, S.; Yang, J.; Zhang, J.; Luo, J.; Grin, Y.; Zhao, J.-T.
• Is Part Of: Materials today physics. Volume 21(2022)
• Publication Date: 2021-11
• Subjects: Zintl phase -- Lattice thermal conductivity -- Crystal structure -- Chemical composition -- Chemical bonding; Materials science -- Periodicals; Physics -- Periodicals; Electronic journals; 530.41
• DOI: 10.1016/j.mtphys.2021.100480
• Languages: English
• ISSNs: 2542-5293

Abstract

Abstract: The intrinsically low lattice thermal conductivity κ L is essentially important for thermoelectric technology to maintain large working temperature difference, in order to enlarge the output power. In principle, high density and complex structure at atomic and nano scale are typical features for thermoelectric materials with low lattice thermal conductivities ( κ L s). However, many 122-phase Zintl compounds with promising thermoelectric properties defy these paradigms. They adopt three relatively simple structures with comparably small mean atomic mass, while these compounds exhibit considerably low lattice thermal conductivities κ L s. Herein we unveil the origins of low κ L s in 122-phase Zintl compounds, ascribed from the important aspects including atomic constituents, their arrangements and chemical bonding. The coupling between the acoustic branches and low-frequency optical branches, as well as the anisotropic chemical bonding are responsible for the high anharmonicity, favoring for the low phonon velocity and small relaxation time. This work offers a guidance to design high-performance Zintl thermoelectric materials with ultralow lattice thermal conductivity. Graphical abstract: Image 1 Highlights: The lattice thermal conductivities of 122-phase Zintl compounds were summarized. Low κ Ls originate from element constitute, atomic arrangement and chemical bonding. The coupling between the acoustic branches and low-frequency optical branches favors low κ L . Anisotropic chemical bonding are responsible for the strong anharmonicity.