Hf Incorporation in (Ti,Zr)NiSn Half Heusler Solid Solutions via Mechanical Alloying

Half Heusler materials are promising thermoelectric materials with potential application in generators at medium range temperatures. Solid solutions are typically prepared by arc melting, presenting interesting properties. In this work, the effect of Hf incorporation and the formation of solid solutions is discussed. More specifically, Ti 1−x Hf x NiSn and (Ti 0.4 Zr 0.6 ) 1−y Hf y NiSn half Heusler materials were synthesized via mechanical alloying and consolidated via hot press sintering. Hf incorportation in the lattice strongly affected the lattice thermal conductivity due to the large mass fluctuation. The power factor and thermoelectric figure of merit was optimized via Sb doping the values of 34 μ W/cmK 2 and 38 μ W/cmK 2 ; 0.72 and 0.76 at 762 K for Ti 0.4 Hf 0.6 NiSn 0.985 Sb 0.015 and (Ti 0.4 Zr 0.6 ) 0.7 Hf 0.3 NiSn 0.98 Sb 0.02 , respectively, were reached.