The Influence of Synthesis Procedure on the Microstructure and Thermoelectric Properties of p-Type Skutterudite Ce0.6Fe2Co2Sb12

We have investigated p-type skutterudite samples with the nominal composition Ce0.6Co2Fe2Sb12 synthesized from elementary constituents by gas atomization and conventional melting, and also those synthesized from ternary and binary phases such as Fe x Co1−x Sb2 and CeSb2, respectively, which were mixed and subsequently ball-milled. We conducted measurements of the temperature-dependent transport properties (Seebeck coefficient, thermal/electrical conductivity) and carried out scanning electron microscope analysis, electron probe micro-analysis and powder x-ray diffraction to obtain information about microstructure and elementary distribution of the phases. We show that the presented synthesis methods each possess particular strengths but ultimately, however, lead to different final compositions of the skutterudite phase and secondary phases, which significantly influence the thermoelectric properties of the material. Material prepared using an educt method gave the best thermoelectric properties with a peak ZT of 0.7. Furthermore, we show that even an apparent homogeneous skutterudite area within the material exhibits varying stoichiometry in each grain even though they conform to the solubility range of cerium in this p-type skutterudite. Moreover, we show that marcasite is preferred as an educt over the arsenopyrite phase and discuss the formation of the p-type skutterudite phase with these synthesis techniques.