How thermoelectric properties of p-type Tl-filled skutterudites are improved

The high-temperature thermoelectric properties of p-type Tl-filled skutterudites TlxFe1Co3Sb12 (x = 0, 0.2, 0.4, 0.6, and 0.8) were examined. While samples with x ≤ 0.4 were single-phase Tl-filled skutterudite, samples with x = 0.6 and 0.8 were composed of two phases: TlxFe1Co3Sb12 (x ≈ 0.4) as the matrix phase and a Tl-Fe-Sb ternary alloy. The thermal conductivity (κ) was reduced effectively by Tl addition, but the secondary phase increased κ slightly. The maximum value of the dimensionless figure of merit ZT (=S2T/ρ/κ, where T is the absolute temperature) was 0.36 at 723 K for Tl0.2Fe1Co3Sb12.