International audienceWe report the evaluation of the thermoelectric performance of polycrystalline p-type SnSe, a material in which unprecedented values of the thermoelectric figure of merit ZT have been recently discovered in single crystals. Besides anisotropic transport properties, our results confirm that this compound exhibits intrinsically very low thermal conductivity values. The electrical properties show trends typical of lightly doped, intrinsic semiconductors with thermopower values reaching 500 mu V K-1 in a broad temperature range. An orthorhombic-to-orthorhombic transition sets in at 823 K, a temperature at which the power factor reaches its maximum value. A maximum ZT of 0.5 was obtained at 823 K, suggesting that proper optimization of the transport properties of SnSe might lead to higher ZT values. These findings indicate that this system represents an interesting experimental platform for the search of highly efficient thermoelectric materials

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.

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