A round robin test aiming at measuring the high-temperature thermoelectric properties was carried out by a group of European (mainly French) laboratories (labs). Polycrystalline skutterudite Co0.97Ni0.03Sb3 was characterized by Seebeck coefficient (8 labs), electrical resistivity (9 labs), thermal diffusivity (6 labs), mass volume density (6 labs), and specific heat (6 labs) measurements. These data were statistically processed to determine the uncertainty on all these measured quantities as a function of temperature and combined to obtain an overall uncertainty on the thermal conductivity (product of thermal diffusivity by density and by specific heat) and on the thermoelectric figure of merit ZT. An increase with temperature of all these uncertainties is observed, in agreement with growing difficulties to measure these quantities when temperature increases. The uncertainties on the electrical resistivity and thermal diffusivity are most likely dominated by the uncertainty on the sample dimensions. The temperature-averaged (300-700 K) relative standard uncertainties at the confidence level of 68% amount to 6%, 8%, 11%, and 19% for the Seebeck coefficient, electrical resistivity, thermal conductivity, and figure of merit ZT, respectively. Thermal conductivity measurements appear as the least accurate. The moderate value of the temperature-averaged relative expanded (confidence level of 95%) uncertainty of 17% on the mean of ZT is essential in establishing Co0.97Ni0.03Sb3 as a high temperature standard n-type thermoelectric material.

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.

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