Thermoelectric properties of Spark Plasma Sintered InxYbyLa0.3-x-yCo4Sb12 skutterudite system

A thermoelectric material with sufficient performance at high temperatures is a key factor for thermoelectric generation from solar-thermal energy (I. R. radiation). In this study, we analyzed CoSb3 skutterudite compounds as a thermoelectric material at high temperatures and synthesized filled skutterudites with two types of filler atoms: 1) Yb- and La-fillers with a different electronegativity (X) from the Sb atoms and 2) the In-filler with nearly the same electronegativity (X) as the Sb atoms. All the samples were sintered with the spark plasma sintering method, and their thermoelectric properties were investigated. From the results, the Yb atoms were the most effective in decreasing the thermal conductivity of this system due to their very different electronegativity (X) value from the Sb atoms and lower melting temperature than that of the La-filler. In addition, In-filled compositions had high power factor values while the In-free composition had the lowest power factor value due to its lower melting temperature. The addition of La atoms for filling was not effective in reducing the thermal conductivity of this filled skutterudite system due to its higher melting point. A maximum ZT value of 0.9 at 782 K was obtained in the In0.1Yb0.2Co4Sb12 specimen.