As an eco-friendly thermoelectric material, Cu 2 SnSe 3 has recently drawn much attention. However, its high electrical resistivity ρ and low thermopower S prohibit its thermoelectric performance. Herein, we show that a widened band gap and the increased density of states are achieved via S alloying, resulting in 1.6 times enhancement of S (from 170 to 277 μV/K). Moreover, doping In at the Sn site can cause a 19fold decrease of ρ and a 2.2 times enhancement of S (at room temperature) due to both multivalence bands' participation in electrical transport and the further enhancement of the density of states effective mass, which allows a sharp increase in the power factor. As a result, PF = 9.3 μW cm −1 K −2 was achieved at ∼800 K for the Cu 2 Sn 0.82 In 0.18 Se 2.7 S 0.3 sample. Besides, as large as 44% reduction of lattice thermal conductivity is obtained via intensified phonon scattering by In-doping-induced formation of multidimensional defects, such as Sn vacancies, dislocations, twin boundaries, and CuInSe 2 nanoprecipitates. Consequently, a record high figure of merit of ZT = 1.51 at 858 K is acquired for Cu 2 Sn 0.82 In 0.18 Se 2.7 S 0.3 , which is 4.7-fold larger than that of pristine Cu 2 SnSe 3 .

Bi 2 Te 2.7 Se 0.3 (BTS) is known to be the unique ntype commercial thermoelectric (TE) alloy used at room temperatures, but its figure of merit (ZT) is relatively low, and it is vital to improve its ZT for its wide applications. Here, we show that incorporation of an appropriate amount of GaAs nanoparticles in BTS not only causes the large enhancement of Seebeck coefficients because of energy-dependent carrier scattering, but also gives rise to drastic reduction of lattice thermal conductivity κ L . Specifically, ultralow κ L ∼ 0.27W m −1 K −1 (at 300 K) is achieved for the composite sample incorporated with a 0.3 wt % GaAs nanophase, which is proved to originate mainly from the intensified phonon scattering by the GaAs nanoinclusions and interfaces between the GaAs and BTS matrix. As a result, a maximum ZT = 1.19 (∼372 K) and an average ZT ave = 1.01 (at T = 300−550 K) are reached in the composite sample with 0.3 wt % GaAs nanoinclusions, which are respectively ∼78% and ∼82% larger than those of the BTS matrix in this study, demonstrating that incorporation of the GaAs nanophase is an effective way to improve TE performance of BTS.

Thermoelectric properties of CuSb 1−x Cd x Se 2 (x = 0−0.08) compounds, prepared by vacuum melting, were studied at temperatures of 300−675 K. The results indicate that Cd doping causes both remarkable increase in the Seebeck coefficient and drastic drop of lattice thermal conductivity. The enhancement of thermopower originates mainly from increase of electronic density of states, while the drop of lattice thermal conductivity can be ascribed to enhanced phonon scattering by introduced impurity (dopant) atoms. As a consequence, thermoelectric figure of merit ZT is improved with a maximum ZT = 0.55 (at 675 K) being reached for CuSb 0.98 Cd 0.02 Se 2, which is around 2.2-fold higher than that of the CuSbSe 2 pristine compound. Our results indicate that Cd substitution is a feasible way to improve thermoelectric performance of the CuSbSe 2 -based system.

As a thermoelectric material, p-type CuSbSe2 has attracted much attention due to its intrinsic low thermal conductivity and environment-friendly constituents. In this work, Sb deficient compounds CuSb1-xSe2 (x=0-0.12) are prepared...

As an ecofriendly thermoelectric material with intrinsic low thermal conductivity, ternary diamond-like Cu2SnSe3 (CSS) has attracted much attention. Nevertheless, its figure of merit, ZT, is limited by its small thermopower (S) and power factor (PF). Here, we show that an increase in thermopower by 63% and a carrier-mobility rise of 81% at 300 K can be simultaneously achieved through 5% substitution of Fe for Sn due to both enhancement of electronic density of states and degeneracy of multiple valence band maxima, which lead to high PF = 10.3 μW·cm–1·K–2 at 823 K for Fe-doped CSS (CSFS). Besides, an ultrahigh PF of 14.8 μW·cm–1·K–2 (at 773 K) and 45% reduction of lattice thermal conductivity (at 823 K) are realized for CSFS-based composites with 0.125 wt % of MgO nanoinclusions, owing to further enhancement of S via energy-dependent scattering and strong phonon scattering by the embedded nanoparticles. Consequently, a maximum ZT = 1 at 823 K is reached for the CSFS/f MgO composite samples with f = 0.125 wt %, which is around 2.5 times larger than that of the CSS compound.

No abstract

Cu12Sb4S13 has aroused great interest because of its earth-abundant constituents and intrinsic low thermal conductivity. However, the applications of Cu12Sb4S13 are hindered by its poor thermoelectric performance. Herein, it is shown that Gd substitution not only causes a significant increase in both electrical conductivity σ and thermopower S but also leads to dramatic drop in lattice thermal conductivity κ L. Consequently, large ZT reaches 0.94 at 749 K for Cu11.7Gd0.3Sb4S13, which is ∼41% higher than the ZT value of undoped sample. Rietveld refinements of XRD results show that accompanying inhibition of impurity phase Cu3SbS4, the number of Cu vacancies increases substantially with substituted content x (x ≤ 0.3), which leads to reduced κ L owing to intensive phonon scattering by the point defects and increased σ arising from the charged defects (V Cu ’ ). Crucially, synchrotron radiation photoelectron spectroscopy reveals substantial increment of electronic density of states at Fermi level upon Gd substitution, which is proven, by our first-principle calculations, to originate from contribution of Gd 4f orbit, resulting in enhancement of S. Our study provides us with a new path to enhance thermoelectric performance of Cu12Sb4S13.

Developing n-type materials with high peak and/or average ZT (ZT is the figure of merit) is an urgent need for the lower ZT of the existing n-type BiTeSe materials compared with the p-type BiSbTe materials. Here, we demonstrate that liquid-phase sintering can lead to lowered thermal conductivity and an improved power factor in n-type Ag2Se, which originates from the greatly lowered electronic thermal conductivity attributed to the decreased mobility and improved Seebeck coefficients because of increased effective mass. Benefiting from this, the maximum ZT (ZTmax) of ∼1.21 and the average ZT (ZTave) of 1.06 are successfully achieved in polycrystalline Ag2Se. In this work, ZTave is the highest reported value, being 26% larger than that of Ag2Se reported. Our work shows that liquid-phase sintering to achieve improved thermoelectric (TE) performance opens a great opportunity for designing prospective thermoelectrics.