Chalcogenide Glasses as Prospective Thermoelectric Materials

Abstract

Despite the fact that glasses have interesting characteristics for thermoelectric (TE) applications, their potential as TE materials has only recently been tested. In a recent article, we focused on glasses based on the Ge 20 Te 80 composition, which has a high Seebeck coefficient, S, showing that in Cu x+y Ge 20Àx Te 80Ày the power factor, S 2 /q (where q is the resistivity), strongly improves with increasing Cu concentration. Herein we report on the preparation of glasses in the Cu-Te-As system and their characterization by x-ray diffraction (XRD), differential scanning calorimetry (DSC), and measurements of q and S. Our preliminary results show that the melt-spinning technique allows us to extend the Cu-Te-As glassy domain and leads to T g values that permit use of these glasses in applications up to 100°C. A maximum S 2 /q value of $100 lW K À2 m À1 was obtained for the Cu 30 As 15 Te 55 composition, confirming the potential of these glasses for TE applications.

Semiconducting glasses: A new class of thermoelectric materials?

“…The lower power factor in mainly due to a higher electrical resistivity (3000 mO m) observed on the bulk in comparison with the initial ribbon [22]. EDS analysis of the bulk material showed a different chemical composition (Cu 32 As 8 Te 60 ) that was most probably due to the use of another melt-spinning equipment (suitable for handling the large quantities needed for the SPS sintering tests but with no precise temperature control under 800 1C) and the evaporation of arsenium and tellurium.…”

“…The inclusion of copper in the As-Te system has been reported to enhance the glassy domain (prepared by conventional melt quenching) [20] and the electrical conductivity of the chalcogenide glasses [21]. Moreover, recent studies on Cu x As 45 À x Te 55 (20 oxo35) glasses prepared by melt spinning show a significant increasing of the vitreous domain when compared with the conventional melt quenching technique, which allowed higher copper concentrations in the glassy materials [22]. Besides, Cu x As 45 À x Te 55 glasses have T g $ 135 1C and T C -T g $ 35-40 1C that permits working temperatures higher than those of the Cu x þ y Ge 20 À x Te 80 À y glasses [22].…”

“…Moreover, recent studies on Cu x As 45 À x Te 55 (20 oxo35) glasses prepared by melt spinning show a significant increasing of the vitreous domain when compared with the conventional melt quenching technique, which allowed higher copper concentrations in the glassy materials [22]. Besides, Cu x As 45 À x Te 55 glasses have T g $ 135 1C and T C -T g $ 35-40 1C that permits working temperatures higher than those of the Cu x þ y Ge 20 À x Te 80 À y glasses [22]. Similarly to the Cu-Ge-Te glasses, the increase of copper concentration leads to an increase of the electrical conductivity, while the Seebeck coefficients remain at high values [22].…”

“…Besides, Cu x As 45 À x Te 55 glasses have T g $ 135 1C and T C -T g $ 35-40 1C that permits working temperatures higher than those of the Cu x þ y Ge 20 À x Te 80 À y glasses [22]. Similarly to the Cu-Ge-Te glasses, the increase of copper concentration leads to an increase of the electrical conductivity, while the Seebeck coefficients remain at high values [22]. An almost doubling of the power factor at 300 K for the best composition (Cu 30 As 15 Te 55 ) is observed, when compared with Cu 27.5 A 2.5 Te 70 , reflecting the significantly decrease of the electrical resistivity (Fig.…”

Comprehensive study of tellurium based glass ceramics for thermoelectric application

“…To overcome this obstacle, there is the possibility of varying the compositions to control the carrier concentration. 11 The Cu-Ge-Te, Cu-Si-Te, Cu-Ga-Te and Cu-As-Te glassy systems were developed by Gonçalves et al 10,12,13 and Lucas et al…”