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As an earth‐abundant, environment‐friendly, and cost‐effective material, tetrahedrite Cu12Sb4S13 has attracted much attention in thermoelectrics (TEs). However, the TE performance of the pristine Cu12Sb4S13 (CSS) is mediocre, thereby much improvement is required. In this work, both the electronic and phonon transports of the CSS are engineered using Ga2Te3 as a dopant. In the results, it is indicated that dual substitutions of Ga for Cu and Te for Sb not only cause the enhancement of power factor via electronic band structure tuning, but also leads to a drop in both the electronic and lattice thermal conductivities. As a result, the total thermal conductivity (κ) decreases to 0.98 W m−1 K−1 at 770 K, which is about 58% that of the pristine CSS, thus improving the TE performance with the highest dimensionless figure of merit value increasing to 0.95 for (Cu12Sb4S13)0.9(Ga2Te3)0.1 at 773 K, 1.9 times that of the pristine CSS (≈0.5 at 770 K). [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials allow us to harvest energy practically from any heat source, including heat that would be otherwise wasted. This huge promise of energy harvesting is contingent on identifying/designing materials having higher efficiency than presently available ones. However, due to the vastness of the chemical space of materials, only a small fraction of potential candidates has been experimentally and/or computationally scanned thus far. By employing an artificial intelligence (AI) approach based on compressed-sensing symbolic regression analysis of experimental data in an active-learning framework, we have not only identified a trend in the materials composition for superior TE performance, but also predicted and experimentally synthesized several high-performing TE chalcogenides. In particular, p-type Cu0.45Ag0.55GaTe2 shows a very high experimental figure of merit (zT) ∼1.90 at 770 K using experimentally measured heat capacity (Cp). The present work demonstrates not only experimental realization of AI-predicted high-zT TE, but also the importance and potential of physically informed descriptors in material science, particularly for relatively small but well-controlled datasets typically available from experiments. [ABSTRACT FROM AUTHOR]

Wingtip vortex is the initial phase of aircraft wake flow that jeopardizes flight safety. Previous studies have focused on the effect of incidence angle on tip vortex flow; thus, investigations on tip vortex in the roll-up stage under crosswind conditions are limited. In the present study, two NACA0012 wings with different tip shapes (round and square) were numerically analyzed to explore the effects of wingtip configurations on tip vortex. In addition, the effects of crosswinds on wingtip vortex evolution were also investigated. It was found that sharp edges of the square wingtip generated a multi-vortex system, resulting in a larger turbulent wake vortex core radius. The lift and vortex strength of the square wingtip were 23% higher and only 12% stronger than those of the round wingtip, respectively. Furthermore, crosswinds changed both the pressure distribution and the vortex structure. Crosswinds made the flow field unstable; hence, upwind lower edge vortices of the square wingtip burst earlier and merged faster. Consequently, the tightness of the upwind vortex of the square wingtip increased, and the corresponding vortex strength was enhanced. The downwind vortex of the square wingtip was weakened by 2.7% under a crosswind velocity of 4 m/s, whereas the downwind tip vortex of the round wingtip was strengthened under the same conditions. [ABSTRACT FROM AUTHOR]

The carrier transport mechanism in most thermoelectric semiconductors is governed by conventional band transport, however, there is an exception in ternary Cu2SnSe4 (CTS) or its based counterparts in which the transport mechanism is dominated by a small polaron hoping model. The sluggish movement of the small polaron greatly suppresses the mobility of the carrier due to the strong coupling of the electron with the phonon, therefore, a proper decoupling is highly necessary. To achieve this goal, herein, InSe bonds are created by incorporating some indium into the cation vacancy in CTS, which effectively balances the transports between electron and phonon. As a consequence, both the electrical property (σ) and thermal conductivity (κ) are optimized in the sample Cu2Sn1−xInxSe4 (x = 0.1), and its thermoelectric performance improves with the highest figure of merit (ZT) of 0.5. This value is ≈52% higher than that of the pristine CTS, proving that incorporation of In in the cation vacancy in CTS is an alternative way to balance the transports between electron and phonon. [ABSTRACT FROM AUTHOR]

AgBiSe2 is a promising thermoelectric (TE) candidate because of its intrinsically low thermal conductivity (κ = 0.4–0.5 W K−1 m−1 at ∼770 K) and optimal n-type carrier concentration (5.85 × 1018 cm−3 at 300 K). However, its TE figure of merit (ZT) is still low (0.3 at ∼770 K). Therefore, it is necessary to further improve its ZT. In this work, the solid solutions (AgBiSe2)1−x(Ag2Te)x (x = 0–0.125) have been designed through simple alloying Ag2Te inspired by the entropy engineering concept, and the TE performance has been further regulated. The analyses show that the exothermic effects related to α/β and β/γ phase transitions weaken, and the transition temperature of β/γ decreases as the Ag2Te content increases, which indicates the stabilization of the cubic γ-phase at high temperatures. Aside from that, the power factor (PF) enhances from 2.91 μW/cm K2 (x = 0) to 3.49 μW/cm K2 (x = 0.075), and at the same time, the lattice thermal conductivity reduces from 0.3 W K−1 m−1 to 0.1 W K−1 m−1 at ∼760 K. This directly improves the TE performance with the highest ZT value of 1.0, which is almost double that of the pristine AgBiSe2. The result suggests that the entropy engineering is a very effective screening method in thermoelectrics. [ABSTRACT FROM AUTHOR]

CuInTe 2 (CIT) is one of the typical ternary chalcogenides known for its characteristic mixed polyanionic/polycationic site defects, making it a subject of continuous interest in the field of thermoelectrics. In this work, we propose a chemical composition modulation strategy for CIT by alloying GeTe and then introducing a copper deficiency (denoted by V Cu ). This strategy aims to unpin its Fermi level ( F r ) and shift F r into the valence band (VB) while simultaneously enabling coupling between the optical and acoustic phonon, thereby providing an extra phonon scattering path at low frequencies. The simultaneous composition regulations not only enhance the carrier concentration ( n H ) to 10 19 -10 20 cm -3 but also significantly reduce the lattice thermal conductivity (κ L ) to ∼0.48 W m -1 K -1 , thus effectively realizing electro-acoustic coordination in the present material. As a consequence, the thermoelectric (TE) performance is remarkably improved with the highest TE figure of merit (ZT) of 1.51 at ∼838 K. This value ranks at a higher level among CIT-based materials, which showcases the great significance of chemical composition modulation.

Cu 2 SnSe 4 (CTS) ternary chalcogenides have potential applications in thermoelectrics for they crystallize in a high-symmetry cubic structure and consist of earth-abundant and eco-friendly elements. However, the pristine CTS does not have optimal thermoelectric (TE) performance (ZT = 0.35 at ∼700 K), so further investigation is required in this regard. In this work, we propose an incorporation of In 2 Te 3 with a defect zinc-blende cubic structure into CTS, aiming to regulate the electronic and phonon transport mechanism simultaneously. The first-principles calculation reveals that the element In favors the residing at a vacancy site as an interstitial atom while Te at the Se site, which leads to band convergence and degeneracy, respectively. As a result, the electrical property improves with a 22% increase in the power factor (PF), and at the same time, the lattice thermal conductivity (κ L ) reduces to 0.31 W K -1 m -1 at 718 K. Synergistic engineering realizes a remarkable improvement in TE performance with the highest figure of merit (ZT) of 0.92 at 718 K. This value is ∼3 times that of the pristine CTS and stands among the highest in the Cu 2 SnSe 4 family so far, which proves that the incorporation of In 2 Te 3 into CTS is a good proposal.

Guided by the concept of "phonon-liquid electron-crystal", many n-type argyrodite compounds have been developed as candidates for thermoelectric (TE) materials. In recent years, the p-type Cu 8 GeSe 6 (CGS) compound has attracted some attention in TEs due to the presence of very strong atomic vibrational arharmonicity inside the sublattice, which is caused by the weak bonding between Cu ions and [GeSe 6 ] 8- . However, its TE performance is still poor, with a ZT value of only 0.2 at 623 K. Therefore, in this work, we propose to engineer both the electronic and phonon transports in CGS by incorporating the species In 2 Te 3 . This strategy tunes the carrier concentration and at the same time increases the phonon scattering on the point defects (In Ge , In interstitial , and Te Se ) and randomly distributed tetrahedra ([InSe 4 ] 5- and [GeTeSe 3 ] 4- ). As a result, the phase transformation at 329 K in CGS is eliminated, and the peak ZT value is enhanced from 0.27 for CGS to ∼0.92 for (Cu 8 SnSe 6 ) 0.9 (In 2 Te 3 ) 0.1 at 774 K; this thus proves that the incorporation of In 2 Te 3 in CGS is an effective way of regulating its TE performance.

The argyrodite compound, Ag 8 SnSe 6 (ATS), which is one of the promising thermoelectric (TE) candidates, is receiving growing attention in thermoelectrics recently. However, its TE performance is still low and phases are unstable as the temperature varies. In this work, inspired by entropy engineering, we eliminate the β/γ phase transformation at ∼355 K via alloying Ga, thus extending its high-temperature cubic phase from 320 to 730 K. In the meantime, the power factor (PF) enhances by 10% and lattice thermal conductivity (κ L ) reduces by 40% at 723 K. As a result, the ZT value is boosted to ∼1.15 for Ag 8 Sn 0.5 Ga 0.5 Se 6 , which stands high among the ATS systems. This proves that the entropy engineering is an effective approach to extend the high-temperature range for the cubic γ-phase and improve its TE performance simultaneously.