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The p-type Te-free Cu3SbSe4 with famatinite structure is a potential candidate for thermoelectric materials due to the low cost and eco-friendly constituent elements. However, its strong bipolar effect and high lattice thermal conductivity (κlat) are the main challenges for its performance enhancement. Herein, we report a new strategy to enhance its figure of merit zT ∼0.86 at 673 K for Cu3Sb0.95Fe0.05Se2.8S1.2 via band structure tuning and hierarchical architecture. Firstly, S substituted Se atoms in lattice can widen the band gap to alleviate the bipolar effect. Secondly, Fe doping in Sb site significantly increases the density of states, thus increasing the carrier effective mass, and obtaining a remarkably high Seebeck coefficient of ∼560 μV/K at 300 K. Moreover, the induced hierarchical architecture defects resulting in a minimum κlat of ∼0.48 W·m−1·K−1 at 673 K. Consequently, the improved Seebeck coefficient combined with low thermal conductivity leads to an enhanced zT.

Cu3SbSe4 is a potential p-type thermoelectric material, distinguished by its earth-abundant, inexpensive, innocuous, and environmentally friendly components. Nonetheless, the thermoelectric performance is poor and remains subpar. Herein, the electrical and thermal transport properties of Cu3SbSe4 were synergistically optimized by S alloying. Firstly, S alloying widened the band gap, effectively alleviating the bipolar effect. Additionally, the substitution of S in the lattice significantly increased the carrier effective mass, leading to a large Seebeck coefficient of ~730 μVK−1. Moreover, S alloying yielded point defect and Umklapp scattering to significantly depress the lattice thermal conductivity, and thus brought about an ultralow κlat ~0.50 Wm−1K−1 at 673 K in the solid solution. Consequently, multiple effects induced by S alloying enhanced the thermoelectric performance of the Cu3SbSe4-Cu3SbS4 solid solution, resulting in a maximum ZT value of ~0.72 at 673 K for the Cu3SbSe2.8S1.2 sample, which was ~44% higher than that of pristine Cu3SbSe4. This work offers direction on improving the comprehensive TE in solid solutions via elemental alloying. [ABSTRACT FROM AUTHOR]

Cu3SbSe4 is a potential p-type thermoelectric material, distinguished by its earth-abundant, inexpensive, innocuous, and environmentally friendly components. Nonetheless, the thermoelectric performance is poor and remains subpar. Herein, the electrical and thermal transport properties of Cu3SbSe4 were synergistically optimized by S alloying. Firstly, S alloying widened the band gap, effectively alleviating the bipolar effect. Additionally, the substitution of S in the lattice significantly increased the carrier effective mass, leading to a large Seebeck coefficient of ~730 μVK−1. Moreover, S alloying yielded point defect and Umklapp scattering to significantly depress the lattice thermal conductivity, and thus brought about an ultralow κlat ~0.50 Wm−1K−1 at 673 K in the solid solution. Consequently, multiple effects induced by S alloying enhanced the thermoelectric performance of the Cu3SbSe4-Cu3SbS4 solid solution, resulting in a maximum ZT value of ~0.72 at 673 K for the Cu3SbSe2.8S1.2 sample, which was ~44% higher than that of pristine Cu3SbSe4. This work offers direction on improving the comprehensive TE in solid solutions via elemental alloying.

Cu 3 SbSe 4 is a promising Te-free p-type thermoelectric material, characterized by earth-abundant, low-cost, and environmentally friendly constituents. Nonetheless, its thermoelectric performance is poor due to its extremely low electrical conductivity (deriving from the low carrier concentration) and high lattice thermal conductivity. Herein, we report a high-performance Cu 3 SbSe 4 -based material by compositing LaCl3 and introducing multiscale structure. The LaCl 3 -composted Cu 3 SbSe 4 forms heterojunctions that facilitate charge accumulation at the interfaces. The redistribution of electrons between the two materials increases the electrical conductivity without damaging the Seebeck coefficient, and thereby significantly improving the power factor to ∼1150 μWm−1K−2 for Cu 3 SbSe 4 -based bulk. Furthermore, the hierarchical architecture defects are induced by LaCl 3 compositing, yielding a minimum κ lat of ∼0.68 Wm−1K−1 at 673 K. As a consequence, a maximum ZT value of ∼0.90 at 673 K is achieved in the Cu 3 SbSe 4 +2 mol% LaCl 3 sample, representing an 80 % improvement compared to the pristine Cu 3 SbSe 4. [Display omitted] • A high-performance Cu 3 SbSe 4 -based material is obtained by compositing LaCl3 and introducing hierarchical architecture. • LaCl 3 compositing induce the formation of phase interfaces, thus synergistically increasing σ and suppressing κ lat. • Hierarchical architecture defects involving point defects, second phase, dislocations, grain boundaries and phase interfaces decrease κ lat. • LaCl 3 compositing boost Cu 3 SbSe 4 to an outstanding ZT value ∼0.90 at 673 K. [ABSTRACT FROM AUTHOR]

Cu 3 SbSe 4 , a promising p-type thermoelectric (TE) material consisting of earth-abundant, nontoxic, cost-efficient and eco-friendly constituent elements. However, its low TE performance is relatively poor because of the low carrier concentration and mobility. Herein, we synergistically optimize the electrical and thermal transport properties of Cu 3 SbSe 4 via embedding nanoscale Sb 2 Se 3. The Sb 2 Se 3 nanophase markedly increases the carrier concentration and carrier effective mass simultaneously, resulting in a higher power factor of ∼1100 μW m−1 K−2. Surprisingly, Sb 2 Se 3 nanophase induces high-density phase boundaries and dislocations, which significantly depress the lattice thermal conductivity. The multiple effects of incorporation of Sb 2 Se 3 boost Cu 3 SbSe 4 to an outstanding ZT value of ∼0.86 at 673 K for Cu 3 SbSe 4 +1.5 mol% Sb 2 Se 3 composite, which is ∼1.70 times as high as that of pristine Cu 3 SbSe 4. It is highly remarkable that Cu 3 SbSe 4 with nanoscale Sb 2 Se 3 is mechanically robust, showing the Vickers hardness (H v) and fracture toughness (K IC) of ∼2.54 GPa and ∼0.73 ± 0.02 MPa m½, which are ∼20% and ∼12% higher than those of pristine Cu 3 SbSe 4 , respectively. This work provides guidance for enhancing the comprehensive TE and mechanical properties of the copper-based chalcogenides by embedding nanophases. The thermoelectric and mechanical properties of Cu 3 SbSe 4 are synergistically optimized via embedding nanoscale Sb 2 Se 3. The enhanced thermoelectric performance due to the increased carrier concentration and depressed lattice thermal conductivity, the improved mechanical performance derived from the dispersion strengthening of Sb 2 Se 3 nanophases. Therefore, the Sb 2 Se 3 composited Cu 3 SbSe 4 exhibits great potential in application. [Display omitted] • The Sb 2 Se 3 nanophases markedly increase the n and m∗of Cu 3 SbSe 4 , resulting in a higher power factor of ∼1100 μW m−1 K−2. • Sb 2 Se 3 nanophases induce high-density phase boundaries and dislocations to significantly depress the κ lat. • The multiple effects of incorporation of Sb 2 Se 3 boost Cu 3 SbSe 4 to an outstanding ZT value of ∼0.86 at 673 K. • Cu 3 SbSe 4 with nanoscale Sb 2 Se 3 is mechanically robust, showing H v and K IC of ∼2.54 GPa and ∼0.73 ± 0.02 MPa m½, respectively. [ABSTRACT FROM AUTHOR]

Cu 3 SbSe 4 , consisting of earth-abundant and inexpensive elements, is a promising p-type thermoelectric (TE) material. However, its thermoelectric performance is low in comparison with typical Pb-based materials. Here, we tune Ag content to optimize synergistically electrical and thermal transport properties for achieving high TE performance of Bi-doped Cu 3 SbSe 4 materials. Dual-incorporation of Bi and Ag spontaneously generates multiple secondary phases involving CuSe and AgSbSe 2. The multiscale defects including point defects, dislocations, nanoprecipitates and grain boundaries can enhance phonon scattering, thereby obtaining a low thermal conductivity (κ) of ~ 0.67 W m−1 K−1 at 673 K. The carrier concentration is improved due to the enhanced Cu vacancies caused by softening of Cu 3d–Se 4p bond after Ag doping, leading to the obviously increased electrical conductivity (σ). Meanwhile, the heavy element dopants (Bi and Ag) can modify the band structure to enhance Seebeck coefficient (S) by enlarging band gap (E g) and increasing carrier effective mass (m *). The simultaneously enhanced σ and S result in a large power factor (S 2 σ) of ~1200 μW m−1 K−2 at 673 K. Consequently, a maximum ZT of ~1.18 (~136% higher than that of pristine Cu 3 SbSe 4) at 673 K and an averaged ZT of ~ 0.51 at 300–673 K are achieved for Cu 2.85 Ag 0.15 Sb 0.985 Bi 0.015 Se 4 sample due to a low κ and a high S 2 σ. This work offers a referential strategy to improve the comprehensive TE performance by dual-incorporation with isovalent heavy element doping for the diamond-like materials. • Cu 3 SbSe 4 -based materials show excellent TE properties through synergistically optimizing σ and κ lat with Bi and Ag co-doping. • The improved σ by the increased n , and S by the large m * and enlarged E g , yielding a high S 2 σ of ~ 1200 μW m−1 K−2. • Defects including point defects, dislocations, nanoprecipitates and grain boundaries, resulting in a low κ of ~ 0.67 W m−1 K−1. • A maximum ZT of ~ 1.18 at 673 K and averaged ZT of ~ 0.51 at 300–673 K are obtained for Cu 2.85 Ag 0.15 Sb 0.985 Bi 0.015 Se 4 sample. [ABSTRACT FROM AUTHOR]

Cu 3 SbSe 4 -based materials have attracted much attention for thermoelectric power generation in the mid-temperature range due to their low cost, ecofriendliness, and abundant elements on the earth. However, the peak figure of merit ( ZT ) for the Cu 3 SbSe 4 -based system prepared by the fusion method is usually smaller than unity because of its high thermal conductivity. Here, we show that through a coprecipitation method combined with spark plasma sintering ultrafine-grained Cu 3 Sb 0.94 Sn 0.06 Se 4- y S y ( y = 0, 0.5) embedded with Cu 3 SbSe 3 nanoprecipitates can be prepared. Due to the ultralow thermal conductivity and enhanced Seebeck coefficient, a record-high ZT value of 1.32 is achieved for the sample Cu 3 Sb 0.94 Sn 0.06 Se 3.5 Se 0.5 . The ultralow thermal conductivity is attributed to the enhanced phonon scattering caused by the nanoprecipitates and fine grains of the samples, and the improved Seebeck coefficient originates from the enhancement of electronic density-of-state effective mass. Present results demonstrate that excellent thermoelectric performance can be realized in dual-substituted and fine-grained Cu 3 Sb 0.94 Sn 0.06 Se 4- y S y with nanoprecipitates.