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

The solubility of Yb in YbxCo4Sb12 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 degrees C in Yb0.35Co4Sb12.