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AgInTe2 compound has not received enough recognition in thermoelectrics, possibly due to the fact that the presence of Te vacancy (VTe) and antisite defect of In at Ag site (InAg) degrades its electrical conductivity. In this work, we prepared the Ag1-xInTe2 compounds with substoichiometric amounts of Ag and observed an ultralow lattice thermal conductivity (κL = 0.1 Wm−1K−1) for the sample at x = 0.15 and 814 K. This leads to more than 2-fold enhancement in the ZT value (ZT = 0.62) compared to the pristine AgInTe2. In addition, we have traced the origin of the untralow κL using the Callaway model. The results attained in this work suggest that the engineering of the silver vacancy (VAg) concentration is still an effective way to manipulate the thermoelectric performance of AgInTe2, realized by the increased point defects and modified crystal structure distortion as the VAg concentration increases. [ABSTRACT FROM AUTHOR]

α-In2Se3 is of large bandgap (∼1.4 eV) semiconductor and its structure is based on two-layer hexagonally packed arrays of selenium atoms with 1/3 of the sites of indium atoms being empty. Here we report a bandgap Eg reduction due mainly to the formation of a Cu2Se slab in the host In2Se3, which is responsible for the remarkable improvement of thermoelectric performance of bulk polycrystalline In2-xCuxSe3 (x = 0.1-0.2). When x = 0.2 the dimensionless figure of merit ZT and power factor were increased by a factor of 2 and 3, respectively, at 846 K if compared to those of Cu-free In2Se3. Interestingly, an incorporation of Cu into the lattice of In2Se3 results in a change in morphology from amorphouslike structure represented by In2Se3 to a visible polycrystalline form attributed to partial crystallization of the structure. This change enhances lattice thermal conductivities κL over the very low values of In2Se3. However, the enhancement is only moderate because of the effective scattering of phonons in the polycrystalline nanostructure. [ABSTRACT FROM AUTHOR]

In this paper we reported the thermoelectric (TE) properties in nanostructured homologous series alloys GamSbnTe1.5(m+n) over the temperature range of 318–482 K and observed the maximum TE figure of merit (ZT) value of 0.98 for the alloy with m:n=1:10 at 482 K, which is approximately 0.24 higher than that of undoped Sb2Te3 at the corresponding temperature. This improvement is mainly attributed to the substantial reduction in lattice thermal conductivity due to the phonon scattering caused partly by the nanograins (<30 nm) and amorphous structure conceived in the matrix and partly by the lattice distortion resulted from an occupation of some Ga atoms in the Sb sites and a certain amount of Ga2Te3 precipitation. If in comparison with the TE properties for Ga directly doped Bi–Sb–Te solid solutions, we conclude that these Bi-free nanostructured homologous series alloys GamSbnTe1.5(m+n) with proper compositions are of great potentiality for the improvement of TE performance. [ABSTRACT FROM AUTHOR]

In this paper we reported the thermoelectric (TE) properties in nanostructured homologous series alloys GamSbnTe1.5(m+n) over the temperature range of 318–482 K and observed the maximum TE figure of merit (ZT) value of 0.98 for the alloy with m:n=1:10 at 482 K, which is approximately 0.24 higher than that of undoped Sb2Te3 at the corresponding temperature. This improvement is mainly attributed to the substantial reduction in lattice thermal conductivity due to the phonon scattering caused partly by the nanograins (<30 nm) and amorphous structure conceived in the matrix and partly by the lattice distortion resulted from an occupation of some Ga atoms in the Sb sites and a certain amount of Ga2Te3 precipitation. If in comparison with the TE properties for Ga directly doped Bi–Sb–Te solid solutions, we conclude that these Bi-free nanostructured homologous series alloys GamSbnTe1.5(m+n) with proper compositions are of great potentiality for the improvement of TE performance. [ABSTRACT FROM AUTHOR]

Cu4Te3 substituted (Cu4Te3)x–(Bi0.5Sb1.5Te3)1-x (x=0–0.2) alloys were prepared using spark plasma sintering technique and their thermoelectric properties were evaluated. Measurements show that the alloy with x=0.025 reveals very high electrical conductivity and low lattice thermal conductivity, the Seebeck coefficient that increases linearly with temperature is dependent on Cu4Te3 concentration. The maximum ZT value of 1.26 for the alloy with x=0.025 is achieved at 474 K, whereas that of the state-of-the-art thermoelectric material Bi0.5Sb1.5Te3 is only 0.58 at 318 K, thus indicating that the currently prepared pseudobinary alloy is very encouraging. [ABSTRACT FROM AUTHOR]

In this work we have observed a remarkable improvement in the thermoelectric (TE) performance of In6- xSn xSe7 ( ZT = ∼0.28 at x = 0.1, 833 K) compared to that of pristine In6Se7 ( ZT = 0.015 at 640 K). This improvement is mainly attributed to the creation of active donor defects SnIn3+ as Sn(4+) is energetically favorable to In+ sites. Although Sn (2+), which generates a defect SnIn− as an acceptor when it is incorporated into the In3+ sites, has a negative effect on the transport properties, the counter effect from Sn(4+) and Sn(2+) suggests that In6Se7-based alloys are prospectively good thermoelectric candidates if their chemical compositions are well optimized. [ABSTRACT FROM AUTHOR]

In this work, we have observed the enhancement of carrier concentration in α-In2Se3 at a specific S content. This enhancement results from avoiding the annihilation of defects, such as VIn and interstitial Ini acting as donors, via the rearrangement of both the cationic and anionic disorders. Therefore, there is a remarkable improvement in electrical conductivity ( σ). For example, the sample α-In2S0.05Se2.95 perpendicular to the pressing direction ( C┴) gives the highest σ value of 5.56 × 103 Ω−1 m−1 at 923 K, while the virgin α-In2Se3 gives only 9.17 × 102 Ω−1 m−1. In addition, there are dual effects on the lattice thermal conductivity ( κL) resulting from the stabilization of the lattice structure caused by the rearrangement of defect disorder and the lattice distortion from the formation of defect SSe. Therefore, the lattice contribution ( κL) in S-incorporated α-In2Se3 remains relatively high at high temperatures. As a consequence, we have improved the thermoelectric performance, achieving a ZT value of 0.67 for α-In2S0.05Se2.95 at 923 K, which is about 2.8 times that of virgin α-In2Se3 ( ZT = 0.24 at C┴). [ABSTRACT FROM AUTHOR]

We synthesized the solid solutions CuGa1-xInxTe2 (x = 0-1.0) by isoelectronic substitution of element In (Ga) for Ga(In) in the CuMTe2 (M = Ga, In) lattices and examined their thermoelectric properties. The structure upon substitution provides much high Seebeck coefficient (α), relatively low thermal (κ), and electrical conductivity (σ). AT 701 K, the α, σ, and κ are 283.15 µV K-1, 1.15 × 104 Ω-1 m-1, and 0.71 W m-1 K-1, respectively, for CuGa0.36In0.64Te2, which give the figure of merit (ZT) of 0.91, about two times those of the mother compounds CuGaTe2 and CuInTe2. This material holds great application perspectives at intermediate temperatures. [ABSTRACT FROM AUTHOR]

In-Sn-Te-based alloys usually have low electrical and thermal conductivity. In the present work we substituted Al for In in an In-Sn-Te alloy and prepared an (InAlTe)(SnTe) alloy by spark plasma sintering. Substitution of Al for In favors the formation of indium impurity levels in this structure and accounts for the decrease of the band gap ( E) and much of the increase of mobility and electrical conductivity. The thermal conductivity decreases from 1.72 W K m to 1.44 W K m with temperature, while that of the (InTe)(SnTe) alloy increases from 2.29 W K m to 3.50 W K m. The thermoelectric figure of merit ( ZT) of the sample increases with measurement temperature, and the highest ZT value of 0.28 was obtained at 668 K, being a factor of 4.5 greater than the maximum ZT value for the Al-free (InTe)(SnTe) alloy at 510 K. [ABSTRACT FROM AUTHOR]

Here, we present the manipulation of the crystal structure defects: an alternative route to reduce the lattice thermal conductivity (κL) on an atomic scale and improve the thermoelectric performance of CuGaTe2. This semiconductor with defects, represented by anion position displacement (u) and tetragonal deformation (η), generally gives low κL values when u and η distinctly deviate from 0.25 and 1 in the ideal zinc-blende structure, respectively. However, this semiconductor will show high Seebeck coefficients and low electrical conductivities when u and η are close to 0.25 and 1, respectively, due to the electrical inactivity caused by an attractive interaction between donor-acceptor defect pairs (GaCu2+ + 2VCu-). [ABSTRACT FROM AUTHOR]

MoS 2 nanosheets with size of several-hundred nanometers were prepared by a hydrothermal intercalation/exfoliation method, then MoS 2 /Bi 2 Te 3 composite nanopowders were prepared by a microwave-assisted wet chemical method using the MoS 2 nanosheets, TeO 2 , Bi(NO 3 ) 3 ·5H 2 O, KOH and ethylene glycol as raw materials. Bulk MoS 2 /Bi 2 Te 3 nanocomposites were prepared by hot pressing the MoS 2 /Bi 2 Te 3 composite nanopowders with MoS 2 nanosheet content ranging from 0 to 17 wt% at 80 MPa and 648 K in vacuum. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicate that MoS 2 and Bi 2 Te 3 did not react each other during the hot pressing. FESEM observation reveals that the MoS 2 /Bi 2 Te 3 composite samples had a more compact microstructure than the pristine Bi 2 Te 3 bulk sample. The MoS 2 phase was relatively randomly dispersed in the composite. At a given temperature, the electrical conductivity of the composites increases first then decreases as the MoS 2 content increases, whereas the Seebeck coefficient of the bulk nanocomposites does not change much. A highest power factor, ~18.3 μW cm −1 K −2 which is about 30% higher than that of pristine Bi 2 Te 3 sample, at 319 K has been achieved from a nanocomposite sample containing 6 wt% MoS 2 . [ABSTRACT FROM AUTHOR]