Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 10: Thermoelectric materials

DS 10.2: Talk

Tuesday, March 17, 2015, 09:45–10:00, H 0111

Enhanced transport properties of rutile oxides — •Denis Music and Jochen M. Schneider — Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

Oxide based thermoelectrics offer potential for high efficiency thermoelectric conversion for harvesting electricity from heat, but suffer from a low power factor due to the low electrical conductivity. We used quantum mechanical calculations to identify alloying elements for RuO2 with enhanced Seebeck coefficient. We probed all 3d and 4d transition metals as well as all lanthanides and identified Fe and La to be the most promising candidates as a manifold increase in Seebeck coefficient was predicted. This materials design proposal was then critically evaluated by measuring the Seebeck coefficient of sputter-deposited thin films. Furthermore, the electrical and thermal conductivity was measured. Saturated RuO2 with Fe and La exhibit not only a fourfold increase in the Seebeck coefficient, but also a decrease in thermal conductivity. This yields the highest power factor reported for RuO2 despite a twofold decrease in the electrical conductivity. Hence, the ab initio predictions regarding the Seebeck coefficient are validated by experiments. Furthermore, Fe and La lead to grain refinement and a more porous morphology. Our results suggest that maximizing the structural distortion of RuO2 by dilute alloying with selected transition metals and lanthanides can increase the Seebeck coefficient and decrease the thermal conductivity by fostering quantum confinement and phonon scattering, respectively. Other rutile oxides, such as MnO2, will also be discussed.