Predication of an ultrahigh filling fraction for K in CoSb_3

摘要

The filling fraction limit (FFL) for potassium in skutterudite CoSb_3 has been investigated by first-principles methods. The FFL is derived by minimizing the formation energy of a reaction that includes the formation of both the filled skutterudite K_yCo_4Sb_(12) and the potential secondary phases KSb and CoSb_2 when doping K into CoSb_3. Our calculations show that K has an ultrahigh filling fraction up to more than 60% in CoSb_3, as compared with those of previously reported fillers such as Sr, Ba, Ca, La, Ce, Eu, and Yb [X. Shi et al., Phys. Rev. Lett. 95, 185503 (2005)]. The extent to which this affects the thermoelectric properties of K-filled skutterudites is discussed.