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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]

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]

Here, we used two elements Cu and Sb as the substitutes for Te in Ga2Te3 and observed a giant enhancement in thermoelectric figure of merit (ZT). This potential substituted Ga2Cu0.05SbxTe2.95-x (x = 0.2) gives the maximum ZT value of 0.5 at 700 K, more than 3 times as high as that of intrinsic Ga2Te3. The enhancement in ZT is attributed to the significantly reduced thermal conductivity caused mainly by the presence of Cu at Ga vacancy planes, and remarkably improved electrical conductivity by the occupation of Sb at Te sites, which increases the carrier concentration and conserves the high mobility. [ABSTRACT FROM AUTHOR]

In this work, we design and synthesize a hybrid structure consisting of Sn-incorporated Cu3SbSe4 and a second phase CuSe, that is, (Cu3Sb1 − xSnxSe4)(CuSe)y (x = 0–0.04, y = 0.3–0.08), and explore the role of each phase on the improvement of the thermoelectric (TE) performance. In the Cu3Sb1 − xSnxSe4 phase, the element Sn residing at the Sb site provides p-type holes while at the same time increasing the point defects and crystal structure distortion. The presence of the second phase CuSe, which is in situ formed within the Cu3Sb1 − xSnxSe4 matrix, not only improves the electrical conductivity but also increases the phonon scattering on the phase boundaries. As a result, the hybrid structure allows the improvement in TE performance with the highest ZT value of 0.37 at ∼600 K for the samples at x = 0.02–0.03 and y = 0.11–0.09, which is about 42% higher than that of pristine Cu3SbSe4. This work reveals us a new method of improving TE performance, that is, through organizing a hybrid structure in Cu3SbSe4-based composites. [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]

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]

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]