Prediction of New Stable Compounds and Promising Thermoelectrics in the Cu–Sb–Se System

Abstract

We study the phase stability and predict as-yet-unreported compounds in the thermoelectric Cu−Sb−Se ternary system. We use a combination of total energies obtained from density-functional-theory-based (DFT) calculations with vibrational entropies from phonon calculations (within the harmonic approximation) and configurational entropies, treated with cluster expansions (CE). The Cu−Sb−Se ternary phase diagram is determined (treating all phases as line compounds) using the grandcanonical linear programming method. We find the following results: (1) we predict the stability of a new previously unknown, zinc blende-based Cu 4 SbSe 5 compound but find that it is thermodynamically stable up to only ∼300 K; (2) we also predict that a Cu 12 Sb 4 Se 13 phase (isostructural with Cu 12 Sb 4 S 13 , but unreported in the Cu−Sb−Se system) appears in the phase diagram at high temperatures (but below the temperatures where the observed Cu 3 SbSe 3 phase is stable); (3) based on quasi-harmonic phonon and band structure calculations, we find that Cu 12 Sb 4 Se 13 has thermal conductivity and an electronic structure that suggests it as a promising thermoelectric material.

Accurate representation of formation energies of crystalline alloys with many components

“…Accurate computational prediction of the mixing enthalpy and configuration entropy would be very instrumental in studying HEAs, as it is hard to experimentally explore different compositions of five or more elements due to combinatorial complexity. The state-of-the-art methodology of computationally assessing the stability of multicomponent crystalline alloys is based on cluster expansion [5,6,7,8], allowing to fit formation energies of binary systems over the entire range of compositions, ternary and quaternary systems [9,10,11,12] over, typically, some subrange of the composition range, and quinary systems at specific points of the composition range [13].…”

Enhanced Thermoelectric Properties of Cu3SbSe3-Based Composites with Inclusion Phases

“…In fact, Cu 3 SbSe 4 which is a p-type semiconductor with a small band gap attracts much more attention [9]. Cu 12 Sb 4 Se 13 is predicted to be a new promising TE material theoretically [10], the structure of which is similar to tetrahedrites Cu 12 Sb 4 S 13 [11], but this compound has not been synthesized yet. Cu 3 SbSe 3 and CuSbSe 2 both have ultralow thermal conductivity that was thought to be governed by a large lattice anharmonicity [12] caused by lone-pair electron of Sb [13].…”

Is Cu3SbSe3 a promising thermoelectric material?

“…6,7 Among these candidates, many binary and multinary selenides with low k have been found to exhibit promising zT values, such as the layered oxide BiCuSeO, 8,9 liquid-like Cu 2Àx Se 10,11 and the recently reported SnSe. 16 Cu 3 SbSe 3 was found to exhibit an ultralow thermal conductivity characterized by a large lattice anharmonicity 17 that was thought to be governed by the lone-pair electrons of Sb 18 and the "part-crystalline part liquid state". In fact, zT about unity has been obtained in Cu 3 SbSe 4 , 14,15 and Cu 12 Sb 4 Se 13 was also theoretically predicted to be a new promising TE material.…”