High Seebeck Coefficient Values Research Articles

Enhanced thermoelectric figure-of-merit in spark plasma sintered nanostructured n-type SiGe alloys

We report a significant enhancement in the thermoelectric figure-of-merit of phosphorous doped nanostructured n-type Si80Ge20 alloys, which were synthesized employing high energy ball milling followed by rapid-heating using spark plasma sintering. The rapid-heating rates, used in spark plasma sintering, allow the achievement of near-theoretical density in the sintered alloys, while retaining the nanostructural features introduced by ball-milling. The nanostructured alloys display a low thermal conductivity (2.3 W/mK) and a high value of Seebeck coefficient (−290 μV/K) resulting in a significant enhancement in ZT to about 1.5 at 900 °C, which is so far the highest reported value for n-type Si80Ge20 alloys.

Development of (Bi,Sb)2(Te,Se)3-Based Thermoelectric Modules by a Screen-Printing Process

In major applications, optimal power will be achieved when thermoelectric films are at least 100 μm thick. In this paper we demonstrate that screen-printing is an ideal method to deposit around 100 μm of (Bi,Sb)2(Te,Se)3-based films on a rigid or flexible substrate with high Seebeck coefficient value (90 μV K−1 to 160 μV K−1) using a low-temperature process. Conductive films have been obtained after laser annealing and led to acceptable thermoelectric performance with a power factor of 0.06 μW K−2 cm−1. While these initial material properties are not at the level of bulk materials, the complete manufacturing process is cost-effective, compatible with large surfaces, and affords a mass-production technique.

Correlation of Microstructural Properties With Thermoelectric Performance of Bi0.5Sb1.5Te3 Films Fabricated by Electroplating

AbstractThis study shows for the first time, the correlation between the microstructural properties (chemical composition and its homogeneity) and the thermoelectric properties for p-type Bi0.5Sb1.5Te3 electroplated films (10-15 μm thickness). High microstructural quality of Bi0.5Sb1.5Te3 electroplated films (a close to stoichiometry chemical composition with its high homogeneity elements distribution) was achieved by using an additive in the plating solution (sodium ligninsulfonate) as a surfactant agent. A fine-grained microstructure of 280 nm to 1μm has been observed for these materials, which half that of the plated films without a surfactant. The thermoelectric properties of electrodeposited Bi0.5Sb1.5Te3 films obtained without microstructural optimisation, show modest Seebeck coefficient values of 20-120 μm/K, electrodeposited film with an optimised microstructure exhibits very high values of Seebeck coefficient of 220-300 μm/K.

Temperature‐dependent hard X‐ray photoemission spectra of ternary Tl compounds with high Seebeck coefficient

AbstractThe temperature dependence of the core‐level and valence‐band electronic structures of TlGaTe2 and TlInSe2 that exhibits high values of Seebeck coefficient has been studied by hard X‐ray photoemission spectroscopy over the temperature range 40–450 K. The relative peak position and peak width for Tl 4f, Ga 2p and Te 3d in TlGaTe2 are determined. It is shown that not only chemical shift defying the peak position but also electron‐phonon interaction responsible for temperature line‐broadening has rather peculiar temperature behaviour that reflects incommensurate phase transition. Thermoelectric power of TlGaTe2 is evaluated and found to be very close to that of TlInSe2. It is shown that Tl 4f spectra of both compounds also display close similarity (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and thermoelectric properties of Mg2Si1−xSnx

Mg2Si1−xSnx (x = 0.2, 0.4, 0.6 and 0.8) thermoelectric materials have been prepared by vacuum melting and melting/hot-pressing methods. The phase structures and electrical transport properties were measured. The relationships between electronic structures and electronic properties are discussed. X-ray diffraction (XRD) showed that the hot-pressed compounds were better formed. The electrical conductivity and Seebeck coefficient measurements showed that the properties of the compounds were dramatically affected by solid solubility. When x= 0.2, the highest electrical conductivity resulted in the highest power factor of 1.32×10−3 W m−1 K−2 at about 500 K, while the highest value of Seebeck coefficient of −459 μV K−1 was obtained at about 450 K for x= 0.6.

Gravitational effects on grain coarsening during liquid phase sintering : R.M.German et al. (Pennsylvania State University, Pennsylvania, USA.) Metall. Mater. Trans A, vol 28A, no 1, 1997, 215–221

The electronic, optical and thermoelectric properties of bulk and surface of CuInTe2 were investigated by first-principles calculation based on full potential linearized augmented plane wave (FP-LAPW) method. The electron-exchange correlation is taken as generalized gradient approximation (GGA). To improve the energy band gap a modified version of semi-local orbital independent potential called modified Becke Johnson (mBJ) potential is used. The calculated energy band gap of CuInTe2 is in good agreement with available experimental and theoretical results. Both the bulk and surface of CuInTe2 is a direct band gap semiconductor, shows a transition along (Γ−Γ) symmetry point. The calculated band gap of surface and bulk within GGA/mBJ are 0.38/0.63 eV and 0.75/1.13 eV, respectively. This shows an optical interaction of materials at UV range, which can exploited as a heterojunction absorptive layer for solar cell materials. The thermoelectric properties were also calculated based on the Boltzmann semi-local transport theory. The flat and sharp bands along (Γ−Γ) in bulk and surface is responsible for high value of Seebeck coefficient and electrical conductivity, respectively. The higher value of Seebeck coefficient and electrical conductivity is a key to enhance the thermoelectric efficiency.

Semiconductivity of thiourea

Abstract As part of an extensive programme on semiconduction in aliphatic molecular crystals, the conduction and thermoelectric powers of thiourea have been reported. Thiourea is found to be a p-type electronic semiconductor, has a very high value of Seebeck coefficient and has a high energy of activation for carrier generation (2.70 ev). The mobility of the charge carriers appears to be somewhat low. The results have been discussed on the basis of the model proposed by Johnson and Lark-Horowitz. Trapping of majority carriers is suggested to be responsible for the observed abnormalities.