Structure And Themoelectric Properties Of Heusler Alloys

Heusler alloys have good themoelectric properties. as well as the advantagesof environment-friendly, no noise, safety, etc.. But higher thermal conductivitycaused the ZT of Heusler alloys lower. In this paper，as the studied subjects, thepreparation, microstructures and thermoelectric properties.of MNiSn-based n-typeHalf-Heusler alloys, MCoSb-based p-type Half-Heusler alloys and Fe₂TiSn-basedFull-Heusler alloy were studied.The experiment results show that, after ball milling, the particle size of alloywas tens of nanomeater. After SPS sintering, the grain size of the alloy grows toabout500nm, but compared to the size of as-cast （50¹00μm）, the size decreasedsignificantly. This indicates that the preparation of study plays a significant effect ofgrain refinement.Ti_0.25(Zr_1-xHf_x)_0.75NiSn_0.99Sb_0.01alloy with Ti substitude by Zr and Hf wasprepared. The experiment results show that the thermal conductivity decreasedwhile the Zr, Hf replaced Ti. After ball milling, the alloy appeared the secondaryphases. Because of the secondary phases, the themoelectric properties of the alloywas bad. The ZT was0.3for Ti_0.25(Zr_0.3Hf_0.7)_0.75NiSn_0.99Sb_0.01alloy at700℃.The carrier thermal conductivity, electrical conductivity and carrier con-centration decrease and the Seebeck coefficient, lattice thermal conductivityincrease with Hf increase in Ti_0.25(Zr_1-xHf_x)_0.75CoSb_0.9Sn_0.1alloy. Compared tobulk alloy, the thermal conductivity reduced by50%forTi_0.25(Zr_0.3Hf_0.7)_0.75CoSb_0.9Sn_0.1alloy. The alloy with Hf content of0.6had thebest ZT0.4at700℃.The thermal conductivity of Fe₂Ti_1-xHf_xSn alloys decreased with Ti replacedby Hf. The alloys appeared the secondary phases with Hf increase, and thesecondary phases caused the Seebeck coefficient decrease. Fe₂Ti_0.7Hf_0.3Sn alloyhad the best ZT at200℃。...