  This work presents theoretical calculations of the electrical transport
properties of the Ag, Au, and La fractionally filled bulk skutterudites: CoSb3,
CoAs3, and CoP3. Density functional theory (DFT), along with projector
augmented wave (PAW) potentials, was used to calculate bulk band structures and
partial density of states. The Seebeck coefficient (S), electrical conductivity
(s), and power factor (S2 s) were calculated as a function of temperature and
filling fraction using the momentum matrix method along the entire first
Brillouin zone. Calculated trends in the electrical transport properties agree
with previously published experimental measurements for p-type unfilled and La
filled CoSb3. The calculated S and s values for the Ag and Au filled compounds
indicates that the most promising electronic properties are exhibited by p-type
Au0.125(CoSb3)4, Au0.25(CoSb3)4, and Au(CoSb3)4. Au is therefore recommended as
a promising filler for improved thermoelectric properties in cobalt
antimonides. Ag is also a good filler for cobalt phosphides; the creation of a
negative indirect band gap is observed in Ag(CoP3)4, which indicates
semimetallic behavior, so this compound may possibly exhibit lower thermal
conductivity than metallic CoP3. Finally, we recommend future directions for
improving the thermoelectric figure of merit of these materials.
