Remarkable Thermoelectric Performance in K₂CdPb Crystals with 1D Building Blocks via Structure Particularity and Bond Heterogeneity

Abstract

Identifying approaches that reduce thermal conductivity with little impact on electrical transport performance remains a central challenge for the thermoelectric community. Here, we use density functional theory calculations to demonstrate that K 2 CdX (XSn, Pb), with a crystal structure composed of a one-dimensional zigzag Cd-X chain sublattice and an isolated alkali metal K atom, exhibits favorable electronic and phonon transport as well as superior thermoelectric conversion efficiency. We reveal that the presence of a long-range ionic bond and multiple band characteristics lead to "electron crystal"-like electrical transport performance. On the other hand, the ultralow lattice thermal conductivity (κ L ) of the K 2 CdX compound mainly originates from the strong structural anharmonicity, which is caused by a lowdimensional sublattice combined with the heterogeneity of a weak chemical bond and the rattling vibration of K atoms in a crystal matrix. As a result, high average carrier mobility (>20 cm 2 V −1 S −1 ), low lattice thermal conductivity below 0.4 W/mK, and spectacularly high average zT larger than 2.0 predicted for the K 2 CdPb system highlight the direction for identifying compounds with potential thermoelectric performance in this crystal family. KEYWORDS: K 2 CdPb (K 2 CdSn) crystal, 1D zigzag atomic chain, rattlerlike K atoms, anisotropic electrical and thermal transport, thermoelectric performance, first-principles calculations, Boltzmann transport theory

The effect of four-phonon interaction on phonon thermal conductivity of hexagonal VTe2and puckered pentagonal VTe2

“…Thus, the bonding of the PP-VTe 2 monolayer is a mixture of ionic and covalent bonds, and such heterogeneity suggests a more anharmonic lattice. 47 It supports the view that the anharmonicity of the PP-phase structure is significantly stronger than that of the H-VTe 2 monolayer. Therefore, the larger phase space and Gru ¨neisen parameter in PP-VTe 2 make it has relatively large scattering rates, resulting in a relatively low k L in the PP-VTe 2 monolayer with complex structures when only considering the threephonon interaction.…”

Antibonding p-d and s-p Hybridization Induce the Optimization of Thermal and Thermoelectric Performance of MGeTe3 (M = In and Sb)

“…The accuracy of this method has been confirmed by comparison with state-of-the-art electron–phonon coupling results []. In addition, a great deal of work on (Ba, Sr)­SnS 3 [], K 2 CdPb [], CuTaS 3 [], Ca 4 (Sb, Bi) 2 O [], and Cs 3 Cu 2 I 5 [] using the same scheme to estimate the transport properties of the compounds also establishes the applicability of this approach to our system. We adopt a 12 × 12 × 9 k -mesh and mBJ-corrected functional to determine the wavefunction and energy eigenvalues.…”

“…On the other hand, the inherent low κ L in materials may decouple electron and phonon transport as it offers independent control over the electronic transport properties to achieve a balance by regulating the band structure near the Fermi level ( E F ) [ , ]. The crystal structure with low thermal conductivity can be attributed to the strong anharmonicity, which stems from factors such as weak chemical bonds [], resonant bonding [ , ], bonding hierarchy [], and intrinsic rattling atoms [ − ]. The typical representatives of SnSe [ ,, ], BiCuSeO [ , ], PbTe [ , ], and CsAg 5 Te 3 [] all show intrinsically peculiar crystal structures and chemical bond characteristics and demonstrate great potential for high ZT performance.…”

Thermal and Electronic Properties of Ba2MnSe3

“…In contrast, Mn atoms exhibit spin-dependent electron localization, with primarily ionic and electron-gas-like covalent bonding for Mn2 and Mn1, respectively (see Figure ). This bonding “heterogeneity” can affect phonon propagation − and contribute to the low κ for this material.…”