Publications in Scientific Journals:

R.C. Mallik, R. Anbalagan, G. Rogl, E. Royanian, P. Heinrich, E. Bauer, P. Rogl, S. Suwas:
"Thermoelectric properties of Fe0.2Co3.8Sb12-xTex skutterudites";
Acta Materialia, 61 (2013), 6698 - 6710.

English abstract:
Skutterudites Fe0.2Co3.8Sb12−xTex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were synthesized by induction melting at 1273 K, followed by annealing at 923 K for 144 h. X-ray powder diffraction and electron microprobe analysis confirmed the presence of the skutterudite phase as the main phase. The temperature-dependent transport properties were measured for all the samples from 300 to 818 K. A positive Seebeck coefficient (holes are majority carriers) was obtained in Fe0.2Co3.8Sb12 in the whole temperature range. Thermally excited carriers changed from n-type to p-type in Fe0.2Co3.8Sb11.9Te0.1 at 570 K, while in all the other samples, Fe0.2Co3.8Sb12−xTex (x = 0.2, 0.3, 0.4, 0.5, 0.6) exhibited negative Seebeck coefficients in the entire temperature range measured. Whereas for the alloys up to x = 0.2 (Fe0.2Co3.8Sb11.8Te0.2) the electrical resistivity decreased by charge compensation, it increased for x > 0.2 with an increase in Te content as a result of an increase in the electron concentration. The thermal conductivity decreased with Te substitution owing to carrier-phonon scattering and point defect scattering. The maximum dimensionless thermoelectric figure of merit, ZT = 1.04 at 818 K, was obtained with an optimized Te content for Fe0.2Co3.8Sb11.5Te0.5 and a carrier concentration of ∼n = 3.0 1020 cm−3 at room temperature. Thermal expansion (α = 8.8 10−6 K−1), as measured for Fe0.2Co3.8Sb11.5Te0.5, compared well with that of undoped Co4Sb12. A further increase in the thermoelectric figure of merit up to ZT = 1.3 at 820 K was achieved for Fe0.2Co3.8Sb11.5Te0.5, applying severe plastic deformation in terms of a high-pressure torsion process.

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