Thermoelectric and mechanical performance of NiTiAl Heusler compound

Abstract

In the current study, the NiTiAl exhibited the combination of full Heusler (f-Heusler) and Half-Huesler (h-Heusler) phases. The NiTiAl sample was prepared by arc-melting followed and spark plasma sintering at 1073K. The synthesized sample exhibited p-type semiconductor behaviour having a Seebeck coefficient of 50 μV/K at 790K. Further, the resulting power factor is 1.15mWm−1K−2 at 790 K, which is 115% higher than the TiCoSb. The enhancement in power factor is good in agreement with the increased electrical conductivity and measured carrier concentration (nH) ∼ 1020 cm−3. On the other hand, NiTiAl exhibited a hardness value of 7.8 GPa and the estimated fracture toughness (Kc) is 12% higher than the conventional 18 VEC of TiCoSb. Further, the NiTiAl exhibited a low value of κl ∿1.15 Wm−1K−1 at 473K, due to the phonon-phonon scattering of the h-Heusler/f-Heusler interfaces with increasing temperature. However, due to the presence of a larger fraction of metallic f-Heusler phase, the κe is increased significantly and that led to a higher κ, resulting in lower zT∿0.007 at 473 K. Finally, the acquired results of NiTiAl Heusler compound with 17 VEC will open a door for unexplored compounds than the conventional 18 VEC, which could help the thermoelectric community.