Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 41: Thermoelectric materials III: Heterostructures (Focused session – Organizers: Meyer, Heiliger)

DS 41.4: Talk

Friday, March 30, 2012, 10:15–10:30, H 2032

Thermal conductivity in Pr_1−xCa_xMnO₃ and SrTiO₃ thin film systems — •Stefanie Wiedigen¹, Thilo Kramer¹, Manuel Feuchter², Kodanda R. Mangipudi¹, Jörg Hoffmann¹, Marc Kamlah², Cynthia A. Volkert¹, and Christian Jooss¹ — ¹Institute for Materials Physics, University of Göttingen, Germany — ²Institute for Applied Materials, Karlsruhe Institute of Technology, Germany

Epitaxial multilayers and superlattices are one recent approach for the design of efficient thermoelectrics. To study the effect of phonon blocking and scattering on thermal conductivity of oxide multilayers, a combination of two perovskites with promising thermoelectric properties is selected: the orthorhombic Pr_1−xCa_xMnO₃ and the cubic SrTiO₃. In order to investigate the effect of microstructure, interfaces and acoustic impedance mismatch on thermal conductivity κ high preparation quality is needed. Our thin films were prepared by ion-beam and magnetron sputtering. Structural analysis is done by XRD and TEM and will be presented in combination with thermal conductivity measurements using the 3ω method. Single layers of Pr_1−xCa_xMnO₃ show low κ values and no significant increase of thermal conductivty with increasing doping. In homoepitaxial single layers of SrTiO₃ preparation conditions have a high impact on κ, most probably due to different concentrations of point defects. Pr_1−xCa_xMnO₃/SrTiO₃ multilayers show a κ decreases systematically with increasing number of double layers. The results are discussed in the light of the theoretically calculated phonon dispersion and the experimentally observed microstructure.