Dresden 2014 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 42: Thermoelectric Materials

DS 42.10: Vortrag

Donnerstag, 3. April 2014, 17:30–17:45, CHE 89

Simulation Study on Thermoelectric Half Heusler Materials — •Heiko G. Schoberth, Heike Emmerich, and Thomas Gruhn — Material- und Prozesssimulation, Universität Bayreuth, 95447 Bayreuth, Germany

One major task in the development of new thermoelectric materials is to increase the figure of merit by lowering the thermal lattice conductivity. This can be achieved with nanostructured thermoelectrics, in which the phonons are damped at the cluster interfaces. Of special technological interest of thermoelectric materials are CoSb- or NiSn-based half Heusler compounds, in which a complex domain structure forms by partial demixing of the material during the production process [T. Graf et. al., Scripta Mater. 63, 625 (2010)]. We have studied the miscibility of (Ti,Z)CoSb with Z=Cr,Fe,Mn,V,Sc and (Ti,Zr,Hf)NiSn with the help of ab initio calculations. On the one hand, (Ti,Z)CoSb does not show a miscibility gap in the equilibrium state. Therefore, domain structures found in the experiments must result from the preparation method. On the other hand, demixing is found for (Ti,Zr)NiSn and (Ti,Hf)NiSn, while (Zr,Hf)NiSn mixes. We have used a cluster expansion method which provides pseudo-hamiltonians from the first-principles calculations. They are used to perform Monte Carlo Simulations to analyze statistical properties and the phase diagram of the systems, as well as the structure of the domain boundaries. The results will enter later on into phase field simulation to cover the full range from atomistic to micrometer length scale.