Enhanced Thermoelectric Properties of Cu₂SnSe₃-Based Materials with Ag₂Se Addition

Abstract

In this work, (Ag, In)-co-doped Cu 2 SnSe 3 -based compounds are prepared using a self-propagating high-temperature synthesis process. Ag 2 Se and as-synthesized (Ag, In)-co-doped Cu 2 SnSe 3 -based powders are mixed in a proportion according to the formula of Cu 1.85 Ag 0.15 Sn 0.91 In 0.09 Se 3 /x Ag 2 Se (x = 0, 3, 4, and 5%), which is followed by a subsequent plasma-activated sintering (PAS) to obtain consolidated composite bulks. A sandwich experiment is designed to reveal the evolution of the microstructure and phase composition of the composite samples during the PAS process. We investigate the reaction mechanism between Ag 2 Se and Cu 2 SnSe 3 -based matrix as well as the influence of Ag 2 Se on the phase composition, microstructure, and thermoelectric transport properties of the composites. Ag 2 Se addition is proven to be effective to improve Ag solubility in the Cu 1.85 Ag 0.15 Sn 0.91 In 0.09 Se 3 matrix and introduce a CuSe secondary phase and an Ag-rich phase at grain boundaries. The electrical conductivity of Cu 1.85 Ag 0.15 Sn 0.91 In 0.09 Se 3 /x Ag 2 Se (x = 0, 3, 4, and 5%) composites decreases while the Seebeck coefficient increases with increasing Ag 2 Se addition, resulting in an optimized power factor. Moreover, benefiting from the collective phonon scattering at various defects induced by Ag 2 Se addition, the composite samples exhibit significantly suppressed lattice thermal conductivity, which reaches as low as 0.11 W m −1 K −1 at 700 K for the x = 5% sample. A peak figure-of-merit (ZT) of 1.26 at 750 K and an average ZT of 0.75 at 300−800 K are obtained for Cu 1.85 Ag 0.15 Sn 0.91 In 0.09 Se 3 /5% Ag 2 Se. This work provides an efficient way to improve average ZT values of Cu 2 SnSe 3 -based compounds for promising power generation at intermediate temperatures.

Incorporating Controlled Porosity in a Cu2SnSe3 Material To Enhance Its Thermoelectric Properties

“…62 As a result, we achieved an ultralow lattice thermal conductivity value of 0.16 W m −1 K −1 at 548 K for the H3 sample, which is significantly lower than previously reported values as shown in Figure S8. 44,56,63,64 To assess the impact of pores on the reduction of thermal conductivity, two models were employed: the effective medium theory (EMT) and Maxwell-Eucken 1 (M-E 1). 65,66 In the context of the Maxwell-Eucken (M-E 1) model, it is used to figure out the highest possible effective thermal conductivity of a composite material made of two or more different phases (i.e., continuous phase or dispersed phase).…”

“…Furthermore, the presence of a secondary phase, CuSe, and a Ag-rich phase at the grain boundaries was identified as promising phonon scattering centers within the composite. As a result, the thermal conductivity of the Cu 2 SnSe 3 -based composite exhibited a remarkable reduction, up to 0.5 W m −1 K −1 achieved at 700 K. 44 Despite this progress, a further reduction in thermal conductivity is desirable for Cu 2 SnSe 3 -based materials to achieve high ZT. One effective way to reduce thermal conductivity is to introduce porosity as it increases phonon scattering at pore sites.…”

Insights into the Classification of Nanoinclusions of Composites for Thermoelectric Applications

“…Thermoelectric phases added as nanoinclusions directly affect the PF on the basis of their carrier properties and the matrix phase; however, they reduce κ. Various thermoelectric phases such as CoSb 3 , ,,, PbTe, ,, ZnTe, SnTe, MnTe, ZnSb, Cu 2 CdSnSe 4 , PbS, Cu 2 Se, ,, Cu 2 Te, Ag 2 Te, , Ag 2 Se, FeSb 2 , MoSi 2 , MoS 2 , , full-Heusler, , Bi 2 Te 3 , CuInTe 2 , Mg 3 Sb 2 , and Bi 2 Se 3 are used as nanoinclusions. Generally, these secondary thermoelectric-based nanoinclusions are mostly added through the in situ precipitation method. ,, Secondary thermoelectric nanoinclusions with a higher efficiency than the matrix phase are preferred to retain or increase electrical properties and reduce κ .…”

“…(f) Electrical conductivity; (g) Seebeck coefficient; (h) thermal conductivity; and (i) ZT of the Cu 2 SnSe 3 /Ag 2 Se composite. Reprinted with permission from ref . Copyright 2022 American Chemical Society.…”

Theoretical Study of Intrinsic and Extrinsic Point Defects and Their Effects on Thermoelectric Properties of Cu2SnSe3

“…Ecofriendly thermoelectric material Cu 2 SnSe 3 , with a zinc blende structure, has attracted extensive attention due to its constituents being abundant and free of Pb or Te. − A lot of experimental studies have been performed to improve its thermoelectric performance. − For instance, Hu et al reported that they improved its thermoelectric performance due to enhanced crystal symmetry via Mg doping and intensified phonon scattering from dislocations and nano-precipitates; Ming et al reported a large ZT = 1.51 in the Cu 2 Sn 0.82 In 0.18 Se 2.7 S 0.3 sample through comprehensive band structure regulation and introduction of multi-dimensional defects; and a record high ZT = 1.61 was obtained in our previous work by creating high-dense stacking faults and endo-grown nanoneedles to block mid- and low-frequency phonons in Cu 2 SnSe 3 .…”