Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 11: Magnetic Heuslers, Half-Metals and Oxides (jointly with MA)

TT 11.10: Talk

Monday, March 16, 2015, 12:00–12:15, H 0112

Phase separation in NiSn- and CoSb-based Half-Hesleur alloys — Joaquin Miranda Mena, •Heiko G. Schoberth, Thomas Gruhn, and Heike Emmerich — Material- und Prozesssimulation, Bayreuth University. Universitätsstraße 30 D-95448 Bayreuth, Germany

We combine DFT calculations, Monte Carlo simulations and mean field models to study the thermodynamic conditions for phase separation in two families of quaternary-Half-Heusler alloys. In the first family, γNiSn (γ =TiHf, TiZr), we found that phase separation is achieved in the range 500-700 K, but no phase separation is present when alloying with γ=ZrHf. For CoTi(1-x)ZxSb (Z=Sc, Cr, Mn, Fe, Cu) we found transition temperatures in the range 800-3000 K. The transition temperature is favored at nearly one third of concentration (x). However, at large x some materials do not present phase separation, but rather a type of crystal order. We discuss these results in the view of thermoelectrics, where apparently induced phase separation enhances the figure of merit.