Papers by Author: Kwan Ho Park

Abstract: Co_4-xFe_xSb_12-ySn_y skutterudites were synthesized by mechanical alloying and hot pressing, and thermoelectric properties were examined. The carrier concentration increased by doping and thereby the electrical conductivity increased compared with intrinsic CoSb₃. Every specimen had a positive Seebeck coefficient. Fe doping caused a decrease in the Seebeck coefficient but it could be enhanced by Fe/Sn double doping possibly due to charge compensation. The thermal conductivity was desirably very low and this originated from ionized impurity-phonon scattering. Thermoelectric properties were improved remarkably by Fe/Sn doping, and a maximum figure of merit, ZT = 0.5 was obtained at 723 K in the Co₃FeSb_11.2Sn_0.8 specimen.

Abstract: Sn-doped CoSb3 skutterudites were prepared by encapsulated induction melting and their electronic transport properties were examined. The Sn dopant generated excess charge carriers, which increased in concentration with increasing Sn doping content. However, the carrier mobility decreased with increasing doping content, indicating a decrease in the hole mean free path by impurity scattering. The Seebeck coefficient decreased and the electrical resistivity decreased slightly with increasing the carrier concentration due to the reduced carrier mobility by impurity scattering. The lattice thermal conductivity was dominant in the Sn-doped CoSb3 skutterudites.

Abstract: In-filled CoSb3 skutterudites (InzCo4Sb12) were prepared and the filling effects on the thermoelectric and transport properties were examined. Seebeck coefficient and Hall coefficient confirmed that all the samples showed n-type conductivity. Temperature dependence of the electrical resistivity suggested that InzCo4Sb12 is a highly degenerate semiconducting material. The thermal conductivity was considerably reduced by In filling and the lattice contribution was dominant.

Abstract: Co1-xFexSb3 skutterudites were synthesized by encapsulated induction melting and their thermoelectric properties were investigated. Single phase δ-CoSb3 was successfully obtained by the subsequent heat treatment at 773K for 24 hours in vacuum. However, δ-CoSb3 was decomposed to FeSb2 and Sb when x≥0.3, which means that the solubility limit of Fe to Co is x<0.3. The positive signs of Seebeck coefficients for all Fe-doped specimens revealed that Fe atoms acted as p-type dopants by substituting Co atoms. Thermoelectric properties were remarkably enhanced by Fe doping and optimum composition was found to be Co0.7Fe0.3Sb3 in this study.

Abstract: The encapsulated induction melting and hot pressing were employed to prepare the Fedoped CoSb3 skutterudites and their thermoelectric properties were investigated. Single phase δ- CoSb3 was successfully obtained by the subsequent heat treatment at 773K for 24 hours. Iron atoms acted as electron acceptors by substituting cobalt atoms. Thermoelectric properties were remarkably improved by the appropriate doping. Co0.7Fe0.3Sb3 was found as an optimum composition for best thermoelectric properties in this work.