Ultralow Lattice Thermal Conductivity and High Thermoelectric Figure of Merit in Dually Substituted Cu₁₂Sb₄S₁₃ Tetrahedrites

Abstract

The thermoelectric properties of dually substituted Cu12−xInxSb4S12.8Se0.2 tetrahedrites are studied in temperature range from 300 to 723 K. The results indicate that dual substitution of In for Cu and Se for S not only causes the enhancement of thermopower S but also gives rise to a significant decrease in lattice thermal conductivity κL. An ultralow κL ≈0.2 W m−1 K−1 is obtained at 723 K in Cu11.95In0.05Sb4S12.8Se0.2 sample due to the enhanced phonon scattering mainly by point defects. Consequently, a high figure of merit ZTmax ≈1.0 is achieved in Cu11.95In0.05Sb4S12.8Se0.2 sample, which is ≈56% larger than that of pristine Cu12Sb4S13, indicating that dual substitution is effective in boosting the thermoelectric properties of tetrahedrites.

Thermoelectric Performance of Tetrahedrite (Cu12Sb4S13) Thin Films: The Influence of the Substrate and Interlayer

“…The relatively low κ value of 0.18–0.24 W m –1 K –1 (Figure b) might have benefited from the increased phonon scattering at the film interface and the intrinsically low thermal conductivity of Cu 12 Sb 4 S 13 . , The zT value for the Cu 12 Sb 4 S 13 thin film deposited on the TFA test chip increased with temperature, reaching a maximum value of ∼0.18 at 460 K. We can only speculate that the zT value for the Cu 12 Sb 4 S 13 thin film deposited on the SiO 2 -coated Si wafer (which had a higher PF value) would be much higher. However, the current value of 0.18 at 460 K is comparable to results reported at 460 K for Cu 12 Sb 4 S 13 bulk materials in recent studies. ,, For further enhancing the thermoelectric performance of Cu 12 Sb 4 S 13 thin films in future research, exploring various doping strategies appears to be a promising avenue. Drawing inspiration from the investigations of polycrystalline Cu 12 Sb 4 S 13 bulk materials, a variety of dopants (e.g., Sn, Ni, Zn, Gd, etc. ,, ) are worthy of investigation for Cu 12 Sb 4 S 13 thin films.…”

“…Benefiting from a large electrical conductivity value and a nondegraded Seebeck coefficient, the thin film deposited on the SiO 2 -coated Si wafer achieved the highest power factor of ∼362 μW cm –1 K –2 at 625 K (Figure c). This PF value is much larger than those observed for Cu 12 Sb 4 S 13 -based bulk materials reported in the past five years (Figure d). ,,− …”

“…The uncertainties in the obtained Seebeck coefficients, electrical conductivities, and power factors were estimated to be 5%, 3%, and 10%, respectively. (d) Comparison of PF in this work to previously published data for Cu 12 Sb 4 S 13 -based bulk materials. ,,− …”

Three-Fold Coordination of Copper in Sulfides: A Blockade for Hole Carrier Delocalization but a Driving Force for Ultralow Thermal Conductivity

“…This leads to an average Cu–S distance ( d normalC normalu − normalS 0em true̅ ) of 2.274/2.288 Å (XRPD/3D ED) and an average S–Cu–S angle ( α normalS − normalC normalu − normalS 0em true̅ ) of 119.64°/119.7° (XRPD/3D ED), equivalent to those found for the Cu atoms in triangular coordination (CN = 3) of sulfur in Cu 4 Bi 4 S 9 (Table S3), another ternary Cu-based sulfide involving Bi 3+ cations. , Such types of Cu triangular planar coordination can also be observed in a few ternary Cu-based sulfides involving a group VA element with a LP and Cu/M ratio ≥1, such as in tennantite (Cu 12 As 4 S 13 ), , tetrahedrite (Cu 12 Sb 4 S 13 ), , and skinnerite (Cu 3 SbS 3 ) , (Table S3). Some of these phases exhibit intrinsically low lattice thermal conductivity due to LPs associated with elements of the group VA and to large anisotropic ADP for Cu atoms ,,− (see discussion on the thermal properties in the last paragraph).…”

Thermoelectric properties of Gd and Se double substituted tetrahedrite

“…This pattern arises from the activation of minority charge carriers (electrons) in the samples at temperatures above 673 K. A similar trend in electronic thermal conductivity (κ E ) has been documented previously. 31,52 Sample x = 0.4 exhibited the highest κ E of 0.89 W m −1 K −1 at 629 K due to low electrical resistivity. Other samples demonstrated lower electronic thermal conductivity compared to this particular sample.…”