First principles study of Skutterudite/Nb interface at high temperatures for thermoelectric applications

Abstract

Thermoelectric devices convert heat energy into electrical energy and are of great importance in the search for clean and sustainable energy. Most studies in this area focus on developing more efficient thermoelectric materials. The performance of a thermoelectric device also depends on the quality and stability of the interface between the thermoelectric material and the electrode material, particularly during high-temperature operations. However, this aspect is not well studied. Skutterudites-based materials are promising thermoelectric materials to be used at high temperatures (usually greater than 800 K). In this project, using a combination of density functional theory-based calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations, we have studied the interface between (001) surfaces of Ba half-filled CoSb3 Skutterudite and (110) Niobium surface, the latter being used as an electrode. Our calculations show that for unfilled CoSb3 surface, Sb rich surface termination is most stable for almost all of the chemical potential of Sb. For Ba0.5Co4Sb12, the Ba or Sb terminations were most stable depending on the Ba and Sb chemical potential. Upon the formation of the interface, we observe that the skutterudite lattice parameters are stretched along the x-y plane. Amongst the interfaces considered in this study, we find that the binding energies are independent of the surface termination. In contrast, for the Ba half-filled ones, we observe that the relative stability of the interfaces depends on the nature of the surface termination. We find that chemical bonds are formed between the Nb and the Sb atoms in the interface for all the cases. Presently, we are performing molecular dynamics simulations to study the stability of the interface at high temperatures.