Search

In this work we have observed the beneficial effect from the solid solution formation on the thermoelectric performance of (Cu 2(1 − x ) Sb 2 x Te)(Ga 2 Te 3 ) 3 upon Sb substitution for Cu. This substitution allows the different occupations of Sb in the crystal lattice, i.e. Sb at Cu sites with x ≤ 0.05 and at Ga sides with x ≥ 0.05, which has resulted in the Pisarenko relation does not exactly capture the measured Seebeck coefficient under assumed effective masses m *. The reduction of the lattice thermal conductivity ( κ L ) has been quantified within the temperature range from room temperature to 723 K. Over the entire composition range, the κ L value is reduced by 33% and 25% at temperature 723 K and 580 K, respectively. This observation is in a good agreement with the theoretical calculation based on the Callaway model used in the solid solutions. Along with the increasing of the mobility and electrical conductivity, the thermoelectric performance has been improved with the highest ZT value of 0.58 at 723 K, which is about double the value of intrinsic (Cu 2 Te)(Ga 2 Te 3 ) 3 . [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]

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]

In Ga 2 Te 3 -rich quasibinary Cd (3 − 3 m ) Ga 2 m Te 3 ( m = 0.75–0.98) system there are two physical phenomena: structural vacancy ( V ) and its related cationic interdiffusion. The former is able to simultaneously govern the carrier, phonon transportations and the bandgap, while the latter merely facilitates the transportation of carrier to some extent. Accordingly, there are multiple transportation behaviors coexisting at a certain m value in this system. These behaviors, which have not only enhanced the carrier concentration ( n ), but have also increased the entropy of the lattice as m value increases, yield the highest thermoelectric figure of merit ( ZT ) of 0.55 at 682 K for m = 0.98. [ABSTRACT FROM AUTHOR]

Thin-film STEGs (solar thermoelectric generators) show promise in effective use of solar energy as a power supply for wireless sensors and microscale devices. This paper reports a simulation procedure that aims to identify desirable heat flow and temperature distribution to improve the performance of thin-film STEGs. The temperature distribution, heat flux, and voltage of a thin-film STEG are simulated using the finite element method, resulting in an optimal design of the substrate, heat conductive layer, and thermoelectric legs of thin-film STEGs. The effect of air convection on the STEG's performance is also studied. Based on the simulation, a thin-film STEG was designed and fabricated, which exhibits an open-circuit voltage of 22 mV. In addition, the experimental results demonstrate that the measured temperature distribution is in good agreement with the simulated result. To minimize the heat loss from the passive region of the device, an improved design was created in an attempt to confine the heat flow within the thermoelectric legs. This improved design resulted in a 21.4% increase of the output voltage. [ABSTRACT FROM AUTHOR]