Enhanced Thermoelectric Performance by Strong Phonon Scattering at the Heterogeneous Interfaces of the Mg₂Sn/Mg₃Sb₂ High-Content Nanocomposite

Abstract

Nano approaches are practical strategies to boost the thermoelectric figure of merit due to the strong phonon scattering from the grain boundaries and nanoinclusions. Here, we have reported a strong phonon scattering at the heterogeneous interfaces of Mg 2 Sn/Mg 3 Sb 2 high-content nanocomposites (HCnCs). As a result, a significantly reduced lattice thermal conductivity of 1.09 W m −1 K −1 was observed in the equimolar Mg 2 Sn/Mg 3 Sb 2 HCnC, 80% lower than pure Mg 2 Sn and 25% lower than pure Mg 3 Sb 2 . As a result, a high ZT ∼ 1.13 at 773 K was achieved in the Mg 2 Sn/Mg 3 Sb 2 HCnC. Furthermore, various defects, including solid solutions, nanoinclusions, and misfit dislocations, were observed in both the Mg 3 Sb 2 phase and the Mg 2 Sn phase through the microstructure characterization.

Insights into the Classification of Nanoinclusions of Composites for Thermoelectric Applications

“…However, extrinsically added Ag 2 Te nanoinclusions in the BST matrix reduce the α due to the enormous σ increment from the carrier concentration and bipolar diffusion; however, ZT enhancement is observed . As shown in Figure d, adding Mg 3 Sb 2 nanoinclusions in the Mg 2 Sn matrix generates strain fields (dislocations) around inclusions and results in solid scattering points for both mid- and high-frequency phonons . From the addition of MnTe to bismuth telluride, Mn atoms doped into bismuth lattice, enhancing the σ and reducing the α .…”

“…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 .…”

“…(d) Strain distribution in the Mg 2 Sn/Mg 3 Sb 2 composite. Reprinted with permission from ref . Copyright 2021 American Chemical Society.…”

“…111 As shown in Figure 8d, adding Mg 3 Sb 2 nanoinclusions in the Mg 2 Sn matrix generates strain fields (dislocations) around inclusions and results in solid scattering points for both midand high-frequency phonons. 118 From the addition of MnTe to bismuth telluride, Mn atoms doped into bismuth lattice, enhancing the σ and reducing the α. 105 A lower carrier concentration in the CoSb 3 than the Yb 0.15 Co 4 Sb 12 matrix reduced the overall carrier concentration of the composite.…”

Enhanced Thermoelectric Performance in SmMg2Bi2 via Ca-Alloying and Ge-Doping

“…Good thermoelectric materials require high power factor and low thermal conductivity. Two strategies are employed for improving the electrical and thermal transport properties of materials: first, to increase the power factor by optimizing the carrier concentration, , band engineering, and improving the carrier mobility; second, to enhance phonon scattering and reduce thermal conductivity by point defects, , nanostructures, , and nanoscale secondary phases. − Benefiting from the abovementioned optimization strategies, the zT values of various thermoelectric materials, such as chalcogenides, − antimonides, , half Heuslers, and silicides, have been significantly enhanced.…”