Vacancy effect of antimony on shear deformation mechanisms of CoSb3 thermoelectric material

Abstract

Skutterudite CoSb3 is one of the most extensively studied thermoelectric materials in the moderate temperature range, but the easily volatilization of element Sb leads to the vacancy defect as well as the poor mechanical properties of CoSb3. To examine the effect of Sb vacancy on its failure mechanisms, we applied shear loads on defective CoSb3 along (0 0 1)/〈1 0 0〉 slip system by using both density functional theory (DFT) and molecular dynamics (MD) simulations. Both DFT and MD simulation results showed that Sb vacancies can remarkably reduce the mechanical strength of CoSb3. When the Sb vacancy fraction is 4%, the mechanical strength decreases 36% compared with that (7.17 GPa) in flawless CoSb3. Sb vacancies lead to incomplete Sb4-rings and Co-Sb frameworks. This would weaken the local rigidity of the structure, accelerating the breakage of Sb4-rings as well as the slippage of the Co-Sb frameworks. The results provide a perspective for better understanding the vacancy effect on the failure mechanisms of skutterudite CoSb3.