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

Abstract

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 ∼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 <10 mΩ.cm2 in both n-type and p-type HH/Ti thermo-elements was realized, which suggests exciting opportunities and possibilities for achieving highly efficient TE based power generation.