Thermoelectric performance of intermetallic FeGa3 with Co doping

Abstract

Investigation on temperature-dependent electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) of intermetallic Fe1−xCoxGa3 (0.005⩽x⩽0.5) compounds are carried out to probe their thermoelectric performance. From resistivity study, it is observed that increase in number of valence electrons introduced by Co doping leads to a change from semiconducting to metallic behavior, which occurs between x=0.05 and 0.125. The characteristics of the Seebeck coefficient show a substantial decrease with the Co doping, due to the modifications in the band gap and the Fermi-level density of states. Analyses of thermal conductivity of the Co doped FeGa3 compounds reveal that thermal transport is essentially due to the lattice phonons. It is also noticed that the low-temperature peak in the lattice thermal conductivity of these compounds is reduced significantly with the increase in Co content, attributing to the enhanced scattering of phonons by point-defects. The value of the figure-of-merit, ZT=(S2/ρκ)T, is estimated for all compounds, and the maximum room-temperature ZT value of about 0.02 was achieved for Fe0.95Co0.05Ga3, and increased further with temperature to the value of about ∼0.05 at 400K.