Characterisation of Electro-Brush Plated Nickel Coatings on P-Type (Zr,Ti)Co(Sn,Sb) Half-Heusler Thermoelectric Materials for Stable Contact Layers

In this study, a highly conductive nickel (Ni) layer was deposited onto a P-type (Zr,Ti)Co(Sn,Sb) half-Heusler (HH) thermoelectric (TE) material using a low-cost electro-brush plating technique. Before depositing Ni on the TE material, the plating process was optimised on a stainless steel (SS) substrate. An optimal medium-rate deposition voltage of 6V was identified on the SS substrate, with the desired thickness, superior mechanical performance, reduced sheet resistance and surface roughness, and enhanced electrical conductivity. The optimised deposition condition was then applied to the P-type (Zr,Ti)Co(Sn,Sb) material, resulting in a Ni layer that significantly enhanced its electrical and thermal stability. After thermal exposure at 500 °C for 10 h, the Ni coating effectively protected the TE surface against oxidation and sublimation, suggesting that the interfacial contact properties of P-type (Zr,Ti)Co(Sn,Sb) TE material can be effectively enhanced by depositing a highly conductive, oxidation-resistant Ni layer using the cost-effective, straightforward electro-brush plating technique.