Thermoelectric properties optimization of Fe2VGa by tuning electronic density of states via titanium doping

Abstract

We report the correlation between thermoelectric properties and electronic band structure of thermoelectric Heusler alloy Fe2V1-xTixGa by comparing experimental measurements with theoretical calculations. The electrical resistivity data show that the semiconducting-like behavior of pure Fe2VGa is transformed to a more metallic-like behavior at x=0.1. Meanwhile, an enhancement of the Seebeck coefficient was observed for all Ti doped specimens at elevated temperatures with a peak value of 57 µV/K for x=0.05 at 300 K. The experimental results can be elucidated by the calculated band structure, i.e., a gradual shifting of the Fermi level from the middle of the pseudogap to the region of valence bands. With optimized doping, the thermoelectric power factor can be significantly enhanced to 3.95 mWm-1K-2 at room temperature, which is comparable to the power factors of Bi2Te3-based compounds. The synergy of thermal conductivity reduction due to the alloying effect and the significant increase of the thermoelectric power factor leads to higher order zT values than that of prime Fe2VGa.