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Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 24: Thermoelectricity

HL 24.8: Talk

Tuesday, March 17, 2015, 11:30–11:45, EW 202

Resistance Fluctuation Spectroscopy on Thermoelectric CoSb3 and Partially Filled YbxCo4Sb12 Skutterudites — •Sven Heinz1, Martin Lonsky1, Marcus Daniel2, Manfred Albrecht2,3, and Jens Müller11Physikalisches Institut, Goethe-Universität, Frankfurt (M), Germany — 2Institut für Physik, TU Chemnitz, Chemnitz, Germany — 3Institut für Physik, Universität Augsburg, Augsburg, Germany

Thermoelectric materials can directly convert heat to electricity. For the efficiency of this conversion to be high, materials have to have a high electrical conductivity and a low thermal conductivity. Pure CoSb3 combines these conflicting properties unusually well. Thermal conductivity can be further reduced by introducing so called “rattling atoms“ that can move relatively freely at interstitial sites, therefore acting as very efficient scattering centers for phonons. We studied how the introduction of Ytterbium as rattling atoms in CoSb3 alters its electronic transport properties. Besides standard transport measurements, like resistivity and hall-effect measurments, resistance fluctuation spectroscopy has been performed. While 1/f-type-noise dominates in the unfilled samples, we found unusually strong Lorentzian spectra and random telegraph noise in the Ytterbium-filled samples and determined characteristic activation energies of the underlying switching processes. The activation energies Ea exhibit a characteristic temperature dependence, i.e. Ea increases from values of about 5 meV at low temperatures to values of up to 250 meV near room temperature, which is close to the gap energy for the pure material.

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