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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]

Abstract: As a p-type semiconductor, Ga2Te5 has very low Seebeck coefficient and thermal conductivity. Cu, Sb co-doped Ga2Te5 based semiconductor was prepared by spark plasma sintering technique, and its band gap was measured decreasing from ΔEg//=1.77eV represented by intrinsic state to 1.50eV. X-ray analysis reveals the material crystallizes in the main phase Ga2Te5, but with Ga2Te3 and Sb2Te3 minor phases precipitated. The Seebeck coefficient increases from 150 (μV/K) to 275 (μV/K) with temperature elevation, while the electrical conductivity decrease from 5.2×103 (Ω-1. m-1) to 2.4×103 (Ω-1. m-1), but still much higher than that of single crystal of Ga2Te5 reported at the corresponding temperature. The great improvement of electrical properties is closely related to the band gap narrowing, even though the impurity phases precipitated can influence the measured band gap value. The highest ZT value of 0.21 was obtained at 631 K for the Cu, Sb co-doped Ga2Te5 based semiconductor. [Copyright &y& Elsevier]

Abstract: A novel ternary Ag-In-Se semiconductor was prepared using spark plasma sintering technique, and its crystal structure and thermoelectric properties were evaluated. XRD analysis and bandgap measurement indicated that this ternary compound crystallizes in a single phase AgIn5Se8 with its bandgap of 1.11 eV, smaller than that of In2Se3, it therefore is of higher electrical conductivity than In2Se3. The highest power factor and thermoelectric figure of merit ZT, thermal conductivity at 863 K are 2.74x10-4 W.K-2 .m-1, 0.61 and 0.39 W.K-2 .m-1, respectively. [Copyright &y& Elsevier]

In this work the chalcopyrite CuIn3Se5−xTex (x = 0~0.5) with space group through isoelectronic substitution of Te for Se have been prepared, and the crystal structure dilation has been observed with increasing Te content. This substitution allows the anion position displacement ∆u = 0.25-u to be zero at x ≈ 0.15. However, the material at x = 0.1 (∆u = 0.15 × 10−3), which is the critical Te content, presents the best thermoelectric (TE) performance with dimensionless figure of merit ZT = 0.4 at 930 K. As x value increases from 0.1, the quality factor B, which informs about how large a ZT can be expected for any given material, decreases, and the TE performance degrades gradually due to the reduction in nH and enhancement in κL. Combining with the ZTs from several chalcopyrite compounds, it is believable that the best thermoelectric performance can be achieved at a certain ∆u value (∆u ≠ 0) for a specific space group if their crystal structures can be engineered. [ABSTRACT FROM AUTHOR]