Impact of electron doping on thermoelectric properties in filled skutteruditeIrSb3

Abstract

We investigated the variation in electronic, thermal, and thermoelectric properties of skutterudite ${\mathrm{IrSb}}_{3}$ upon filling the voids with alkaline (Na or K) or alkaline-earth atoms (Sr or Ba). Specific heat measurements revealed that the fillers donate electrons with high effective mass, which dominate the electric transport properties of the system. Vibrations associated with the filler additionally contribute to the specific heat, and also scatter phonons efficiently in conjunction with the static disorder, giving rise to the reduced thermal conductivity. The dimensionless thermoelectric figure of merit $ZT$ increases with temperature and electron concentration, and reaches to 0.44 for ${\mathrm{Ba}}_{0.4}{\mathrm{Ir}}_{4}{\mathrm{Sb}}_{12}$ at 685 K. The observed features for the filled ${\mathrm{IrSb}}_{3}$ are similar to those of filled ${\mathrm{CoSb}}_{3}$, indicating that $n$-type filled skutterudite antimonides have a potential as good thermoelectric materials universally.