Thermoelectric Properties of Cobalt-Doped β-FeSi2 with SiC Nanoparticle Inclusions

Abstract

Cobalt doping is an effective approach to improve the thermoelectric properties of semiconducting β-FeSi2 materials. Through preparing β-Fe1−xCoxSi2 samples with x ranging from 0.05 to 0.11, an enhanced ZT of about 0.35 could be achieved within quite a wide doping range (8 mol.% to 10 mol.%) at around 950 K. To further improve the thermoelectric performance, a composite structure consisting of a large grain matrix of β-Fe0.92Co0.08Si2 and inert SiC nanoparticle inclusions was intentionally employed to reduce the lattice thermal conductivity. The microstructure and the effects on the thermoelectric properties of β-Fe0.92Co0.08Si2 with various SiC nanoparticle concentrations were explored. The SiC nanoparticles could be well dispersed into the matrix material without significant agglomerations by the powder processing method. However, the thermal conductivity was not considerably reduced while the electrical properties were affected to some extent, resulting in no gain in the ZT. The current results show that it is feasible to prepare high-quality nanocomposites through the powder processing method, and enhanced thermoelectric performance is expected when using other chemically stable inclusions with lower thermal conductivity and smaller size.