Thermoelectric properties in double-filled Ce0.3InyFe1.5Co2.5Sb12 p-type skutterudites

Abstract Indium was added to the p-type Ce 0.3 Fe 1.5 Co 2.5 Sb 12 skutterudite with the goal of increasing its thermoelectric power factor and figure of merit. Indium is soluble in polycrystalline Ce 0.33 In y Fe 1.5 Co 2.5 Sb 12 until y  = 0.08 ± 0.03. Beyond this concentration, InSb nano-inclusions (∼40–200 nm in size) form at the grain boundaries during the shaping stage. Upon indium double-filling the skutterudite, the hole concentration is reduced, the Seebeck coefficient is increased and the maximum dimensionless figure of merit ZT is enhanced by 20% from 0.54 (725 K) in Ce 0.33 Fe 1.5 Co 2.5 Sb 12 to 0.65 (675 K) in Ce 0.35 In 0.08 Fe 1.5 Co 2.5 Sb 12  + nano-InSb. The enhancement of both the Seebeck coefficient and the power factor can clearly be ascribed to the insertion of indium in the skutterudite. No sign of charge carrier energy filtering by InSb nano-inclusions could be evidenced. InSb nano-inclusions rather act as marginal phonon scatterers, leading to a further small thermal conductivity reduction.