Thermoelectric Properties of Heavy Rare Earth Filled Skutterudites Dy y Fe x Co4−x Sb12

Abstract

Heavy rare earth element Dy-filled skutterudites (DyyFexCo4−xSb12) have been synthesized by a melting–quenching–annealing method and sintered by the spark plasma sintering technique. Our results suggest that single-phased DyyFexCo4−xSb12 compounds could be obtained when the Fe content is less than 1.5. The maximum filling fraction of Dy in skutterudites increases with increasing Fe content. We also found significant lattice expansion induced by Fe substitution at Co sites and Dy filling in the voids. The electrical conductivity, Seebeck coefficient, and thermal conductivity have been measured in the temperature range from 300 K to 800 K. The low-temperature Hall coefficient and carrier mobility are reported in the temperature range from 2.5 K to 300 K. The power factor for DyyFexCo4−xSb12 increases with increasing Fe content. A significant reduction in lattice thermal conductivity is observed in heavy rare earth element Dy-filled skutterudites due to the low localized vibrational frequency of Dy that effectively scatters low-frequency lattice phonons. The sample with composition Dy0.41Fe1.45Co2.55Sb12.28 has lattice thermal conductivity as low as 1.05 W m−1 K−1 at room temperature. The thermoelectric figure of merit (ZT) reaches a maximum value of 0.67 at 750 K.