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 Yb_xCo₄Sb₁₂ Skutterudites — •Sven Heinz¹, Martin Lonsky¹, Marcus Daniel², Manfred Albrecht^2,3, and Jens Müller¹ — ¹Physikalisches 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 E_a exhibit a characteristic temperature dependence, i.e. E_a 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.