Solubility study of Yb in n-type skutterudites YbxCo4Sb12 and their enhanced thermoelectric properties

The solubility of Yb in Yb[subscript x]Co[subscript 4]Sb[subscript 12 was reported to be 0.19 in bulk skutterudites made by melting and slow cooling method. Surprisingly we increased x close to 0.5 by a special sample preparation method: ball mill and hot press. We show that a higher Yb concentration not only increases the power factor due to a higher electron concentration but also reduces the thermal conductivity k because of stronger phonon scattering. In this way, we have achieved a dimensionless thermoelectric figure of merit ZT of about 1.2 at 550 °C in Yb[subscript 0.35]Co[subscript 4]Sb[subscript 12].