Phase separation as a key to a thermoelectric high efficiency

Abstract

This work elucidates the possible reasons for the outstanding, but never reproduced thermoelectric properties of the doped Ti_0.5Zr_0.25Hf_0.25NiSn Heusler compounds. The structural investigations done via synchrotron X-ray diffraction measurements and scanning electron microscope measurements, which clearly show that the microstructure consists of three temperature stable C1_b phases with possible semi-coherent interfaces, are presented. The exceptional thermoelectric properties are due to this intrinsic phase separation. It is possible to reproduce the high Figure of Merit values with ZT = 1.2 at 830 K. Furthermore, the influence of doping different elements on the Sn position in this Heusler material system is investigated.