A First-Principles Theoretical Study on the Thermoelectric Properties of the Compound Cu5AlSn2S8

Abstract

A new compound of Cu 5 AlSn 2 S 8 , which contained earth-abundant and environment-friendly elements and had a diamond-like crystal structure, was designed, and its electronic structure and thermoelectric transport properties from 300 K to 700 K were investigated by first-principles calculations, Boltzmann transport equations, and a modified Slack's model. The largest power factors of Cu 5 AlSn 2 S 8 at 700 K were 47.5 9 10 10 W m À1 K À2 s À1 and 14.7 9 10 10 W m À1 K À2 s À1 for p-and n-type semiconductors, respectively. The lattice thermal conductivity of Cu 5 AlSn 2 S 8 was calculated with its shear modulus and isothermal bulk modulus, which were also obtained by first-principles calculations. The lattice thermal conductivity was 0.9-2.2 W m À1 K À1 from 300 K to 700 K, relatively low among thermoelectric compounds. This theoretical study showed that Cu 5 AlSn 2 S 8 could be a potential thermoelectric material.

Effect of Gallium Substitution in Cu3Al1–xGaxSnS5 Nanobulk Materials on Thermoelectric Properties

“…Among these sulfide TE materials, the Cu−Al−Sn−S system has been predicted to possess a low κ lat value based on the ab initio calculation that suggests that the incorporation of a Group IIIA element into the I−IV−VI system will significantly reduce the κ lat via effective phonon scattering owing to its complex crystal structure. 10 Recently, we fabricated a Cu 3 AlSnS 5 (CATS) nanobulk TE material using chemically synthesized CATS nanocrystals and succeeded in achieving a κ lat lower than that exhibited by other C u − M − S n − S systems. 1 Therefore, the κ value of CATS is quite high even though it has an ultralow κ lat , and the ZT value of CATS remains low.…”

“…With these points in mind, Cu–M–Sn–S (M = metal) quaternary TE materials have recently been regarded as suitable candidates. Among these sulfide TE materials, the Cu–Al–Sn–S system has been predicted to possess a low κ lat value based on the ab initio calculation that suggests that the incorporation of a Group IIIA element into the I–IV–VI system will significantly reduce the κ lat via effective phonon scattering owing to its complex crystal structure . Recently, we fabricated a Cu 3 AlSnS 5 (CATS) nanobulk TE material using chemically synthesized CATS nanocrystals and succeeded in achieving a κ lat lower than that exhibited by other Cu–M–Sn–S systems .…”

Nanobulk Thermoelectric Materials Fabricated from Chemically Synthesized Cu3Zn1–xAlxSnS5–y Nanocrystals

“…The reason why Al is incorporated into Cu–Zn–Sn–S nanocrystals is that ab initio calculations predicted that the incorporation of Al into the I–IV–VI system may cause κ lat to decrease. 23…”

“…In a nod to the materials described above, in this study, we attempt to synthesize Cu 3 Zn 1– x Al x SnS 5– y nanocrystals as building blocks for sustainable thermoelectric materials by revisiting materials based on Cu, Zn, Sn, and S. Note that Cu 3 ZnSnS 5– y differs from conventional CZTS. The reason why Al is incorporated into Cu–Zn–Sn–S nanocrystals is that ab initio calculations predicted that the incorporation of Al into the I–IV–VI system may cause κ lat to decrease …”

“…The reason why Al is incorporated into Cu−Zn−Sn−S nanocrystals is that ab initio calculations predicted that the incorporation of Al into the I−IV−VI system may cause κ lat to decrease. 23 ■ RESULTS AND DISCUSSION Morphology and Crystal Structure of Nanocrystals. Cu 3 Zn 1−x Al x SnS 5−y (x = 0−1) nanocrystals with five different compositions were synthesized, which are referred to as Powder_0, Powder_0.25, Powder_0.5, Powder_0.75, and Powder_1 corresponding to x = 0, 0.25, 0.5, 0.75, and 1, respectively.…”