Thermoelectric properties of p-type YbxLayFe2.7Co1.3Sb12 double-filled skutterudites

► By increasing the Yb filling fraction, the lattice thermal conductivity is gradually depressed. ► The Seebeck coefficient decreases while the electrical conductivity increases when increasing the Yb filling fractions. ► The maximum thermoelectric figure of merit is around 0.99, among the highest values in p-type filled skutterudites.