The role of Ga in Ba0.30GaxCo4Sb12+x filled skutterudites

Abstract

Ba_0.30Ga_xCo₄Sb_12+x (x = 0–0.30) skutterudite compounds were synthesized using a melt–quench–anneal–SPS method and the effect of the content of Ga on the structure and thermoelectric properties was investigated. In samples with Ga content x ≤ 0.15, Ga enters the skutterudite voids and its presence seems to stimulate a more homogeneous distribution of the filler species. Samples with Ga content x ≥ 0.20 possess uniformly dispersed nanoinclusions consisting of circular domains of GaSb with a diameter of 20 nm. As the content of Ga increases, the carrier concentration decreases, the Seebeck coefficient increases, and the heat transport is progressively more impeded. The thermoelectric figure of merit of Ba_0.30Ga_xCo₄Sb_12+x is strongly enhanced in comparison to that of Ba_0.30Co₄Sb₁₂ and reaches values in excess of 1.35 at 850 K for Ba_0.30Ga_0.30Co₄Sb_12.30, approximately twice the value of the Ba_0.30Co₄Sb₁₂ sample.