Density-functional band-structure calculations for La-, Y-, and Sc-filledCoP3-based skutterudite structures

Abstract

The crystal structure, thermodynamic stability, and electronic structure of La-, Y-, and Sc-filled ${\mathrm{CoP}}_{3}$ are predicted from density-functional band-structure calculations. The size of the cubic voids in the skutterudite structure is changed much less than the difference in size between the different filling atoms, and we expect that the larger rattling amplitude of the smaller Sc and Y atoms may decrease the lattice thermal conductivity of Sc- and Y-filled structures significantly compared to La-filled structures. The solubility of La, Y, and Sc in ${\mathrm{CoP}}_{3}$ is calculated to be around 5, 3-6 %, and below 1% at 0 K, respectively. Based on similar systems, this is expected to increase considerably if Fe is substituted for Co. Fe substitution is also expected to compensate the increased charge carrier concentration of the filled structures that is seen in the calculated electron density of states. In conclusion, Sc- or Y-filled $(\mathrm{FeCo}){\mathrm{P}}_{3}$ skutterudite structures are promising materials for thermoelectric applications.