Enhancement of Thermoelectric Behavior of La_0.5Co₄Sb_12−xTe_x Skutterudite Materials

In this work, the effects of Te doping on the microstructure and thermoelectric properties of the partially filled skutterudite La_0.5Co₄Sb₁₂ compounds have been examined. La_0.5Co₄Sb_12−xTe_x skutterudite compounds were synthesized by a combination of the mechanical alloying technique and spark plasma sintering processing, which resulted in partial substitution of Te atoms in Sb sites. The XRD results showed that all the Te-doped bulk samples were composed of a major phase of the Co₄Sb₁₂ skutterudite with a small amount of CoSb₂ and Sb as the secondary phases. Thermoelectric measurements of the consolidated samples were examined in a temperature range of 300 K to 800 K (27 °C to 527 °C). With the La_0.5Co₄Sb_11.7Te_0.3 sample, the highest absolute Seebeck coefficient of 300 μV/K was obtained at 404 K (131 °C) and the lowest lattice thermal conductivity of 2 W/mK was achieved at 501 K (228 °C). Moreover, the minimum electrical resistivity of 19.7 μΩm was recorded at 501 K (228 °C) for La_0.5Co₄Sb_11.5Te_0.5 sample. The effect of the secondary phases was negligible for the electrical resistivity, and between 0.5 to 1.6 pct for the thermal conductivity. Thus, the highest figure of merit, ZT = 0.47, was obtained at 792 K (519 °C) for La_0.5Co₄Sb_11.5Te_0.5 sample due to a significant reduction in electrical resistivity and a moderate increase in the absolute Seebeck coefficient.