n-type (Zr,Ti)NiSn half Heusler materials via mechanical alloying: Structure, Sb-doping and thermoelectric properties

Mechanical alloying has been applied, as an advantageous scalable method, to synthesize Ti_1-xZr_xNiSn half Heusler materials. This is the first time a synthesis of single phase n-type Ti_1-xZr_xNiSn half Heusler solid solutions is reported by this technique, along with structural studies and thermoelectric properties. The application of mechanical alloying was successful, as all compositions ranging between x = 0.4–0.8 were in general single phase materials. The lattice thermal conductivity of the series was lower compared to the same compositions prepared by arc melting. Ti_0.4Zr_0.6NiSn exhibited the minimum lattice thermal conductivity of the series and was selected for doping studies with Sb, with the scope to enhance the thermoelectric performance via the power factor modification. Thermoelectric property measurements resulted in a maximum figure of merit of 0.71 at 762K for Ti_0.4Zr_0.6NiSn doped with 1.5% Sb.