Enhancing thermoelectric properties of p-type CoSb3 skutterudite by Fe doping

In this report, we have successfully synthesized thin films of Co1-xFxSb3 (0 <= x <= 0.1) using electrochemical deposition technique. The electrical and thermoelectric properties of CoSb3 thin films have been investigated by varying the concentration of Fe. X-ray diffraction analysis confirms formation of single phase of Co1-xFexSb3 (0 <= x <= 0.05) with increase in lattice parameter indicating incorporation of Fe at the Co site. The X-ray photoelectron spectroscopy study reveals that Fe2+ substitutes Co3+ thus generating excess hole carriers, further confirmed by the positive signs of Seebeck and Hall coefficients. It is noted that the thermoelectric properties are mainly controlled by Fe substitution in terms of increasing carrier effective mass as well as phonon scattering. Fe substitution does not significantly alter the carrier mobility and thus confining the transport properties to be mainly leveraged by carrier concentration. Scanning thermal microscopy is used to study the effect of Fe incorporation on the thermal conductivity of nanostructured Co1-xFexSb3 thin films. Enhanced value of power factor and relatively lower value of average thermal conductivity for Co1-xFexSb3 sample is achieved at an optimized value of 5% Fe, as a result of enhanced electron transport and phonon scattering. Furthermore, the improved thermoelectric performance makes this natural-abundant, non-toxic and cheap CoSb3:Fe material a very promising candidate for low cost thermoelectric energy generation.