Facile fabrication of p- and n-type half-Heusler alloys with enhanced thermoelectric performance and low specific contact resistance employing spark plasma sintering

Half-Heusler (HH) materials have been actively explored for thermoelectric (TE) based power generation applications in the mid-temperature regime. In the current work, we demonstrate the defect engineering in non-stoichiometric HH alloys to realize a state-of-the-art ZT 1 at 873 K for both n-type Zr0.5Hf0.5Ni1-xSn and p-type Zr0.5Hf0.5Co1+xSb0.8Sn0.2 (x = 0.04) compositions. This enhanced ZT leads to high conversion efficiency of -9% with a high output power density similar to 9 Wcm(2) in both the synthesized n and p-type HH alloys, estimated using cumulative temperature dependence model. A time efficient fabrication route of HH device thermo-elements with Ti electrical contacts, employing spark plasma sintering process, is also demonstrated in the optimized defect engineered HH compositions. A low specific contact resistivity of