Thermoelectric properties of zinc-doped Cu₅Sn₂Se₇ and Cu₅Sn₂Te₇

Abstract

High-performance thermoelectric materials are currently being sought after to recycle waste heat. Copper chalcogenides in general are materials of great interest because of their naturally low thermal conductivity and readily...

Electronic Structure- and Entropy-Driven Design of Thermoelectric Chalcogenide Cu5Sn2Se7 Leading to the Optimization of Carrier Concentration and Reduction in Thermal Conductivity

“…It is observed that the total κ of the pristine CSS reduces from 8.18 W K –1 m –1 at RT to 4.06 W K –1 m –1 at 770 K. These values are higher than 5.3 W K –1 m –1 at RT and ∼3.3 W K –1 m –1 at 700 K but lower than 10.0 W K –1 m –1 at RT and ∼4.2 W K –1 m –1 at 750 K . After the incorporation of In 2 Te 3 , the total κ for the sample at x = 0.1 reduces from 3.9 W K –1 m –1 at RT to 1.4 W K –1 m –1 at 770 K, comparable to those of Zn-doped Cu 4 ZnSn 2 Se 7 . However, they are much higher than many of the state-of-the-art TE materials and Cu chalcogenides, which give only ∼1.0 W K –1 m –1 or less at RT. − …”

“…The compound Cu 5 Sn 2 Se 7 (CSS), which consists of affordable, non-toxic, and earth-abundant elements, has a potential for practical application in thermoelectrics if its thermoelectric (TE) performance can be improved remarkably. Although the number of cations is equal to that of anions, there is electron deficiency in CSS, leaving one hole ( p + ) in terms of the valence state of each atom: [Cu 1+ ] 5 [Sn 4+ ] 2 [Se 2– ] 7 × 1 p + , which accounts for its high carrier concentration ( n H ∼ 3.0 × 10 21 cm –3 at room temperature). − Owing to its high n H , CSS has high electrical conductivity and electronic thermal conductivity ( κ e ) with the peak ZT value of only ∼0.13 at 700 K . Therefore, optimization in n H is required to improve its TE performance.…”

“…In recent years, some pioneering works have been done with respect to the CSS. − For instance, by replacing the monovalent Cu with divalent Zn, the n H reduces to 4 × 10 20 cm –3 , and the peak ZT increases to 0.51 at 750 K . This is the biggest improvement to date in this system.…”

Experimentally validated machine learning predictions of ultralow thermal conductivity for SnSe materials

“…These differently doped SnSe materials had their k values calculated from the thermal diffusivity (D), measured by the TA Instruments LASERFLASH DLF-1 system under an ultrapure argon atmosphere, the specific heat (C p ) calculated using the Dulong-Petit method, and the density (r) determined with the Archimedes method via k = DC p r. The experimental error of the thermal conductivity measurement was estimated to be 5% based on prior experience. [42][43][44] The number of data points collected for D depended on the sample stability with relation to the appearance of bubbles on the surface after the hightemperature diffusivity measurement, surface oxidation, and decomposition of material in pellet form into powder; typically we measured from room temperature to 926 K or less. 41 The selected elements Li, Na, Cu, Ag, Au, Ge, Bi, S, Cl, and Br for this study as dopants for SnSe fell in the category of low environmental impact and medium or high abundance on earth.…”

Optical Properties and Lattice Dynamics of Pure and S‐Alloyed Cu–Zn–Sn–Te Semiconductors: First‐Principles Calculations and Raman Scattering

“…In contrast, the investigation of the telluride members of an extended I-II-IV-VI family is rather limited to date [11][12][13][14][15][16] despite their bandgap being more suitable for photovoltaics [17] and the tellurides preferable for applications in thermoelectrics. [18][19][20][21][22] Therefore, CZTTe (or its alloys with CZTS and CZTSe) can also be a more efficient, sustainable, and probably cheaper alternative to Si, CdTe, HgCdTe, PbS, PdSe, etc. in various applications.…”