High thermoelectric performance of Yb0.26Co4Sb12/yGaSb nanocomposites originating from scattering electrons of low energy

n-type filled skutterudite Yb0.26Co4Sb12 composites in which p-type GaSb nanostructured inclusions (5–20 nm) were dispersed were fabricated by an in situ method involving the introduction of metastable void-filling impurity Ga and enrichment of Sb in the synthesis procedure. With the homogeneously dispersed GaSb nanoinclusions, which probably result from the scattering of low-energy electrons by the GaSb-related boundary energy barriers, the power factor is enhanced due to the significant enhancement of the Seebeck coefficient. The total thermal conductivity was decreased with the depression of electronic thermal conductivity. As a result, the dimensionless thermoelectric figure of merit ZT value was improved over a wide working temperature range of 300–850 K, and the expected optimal thermal-electric conversion efficiency ηopt 15.0% was obtained for the Yb0.26Co4Sb12/0.2GaSb nanocomposite.