Exceeding the filling fraction limit in CoSb3 skutterudite: multi-role chemistry of praseodymium leading to promising thermoelectric performance

Abstract

To this date and to the best of our knowledge, praseodymium (Pr), has not been reported for an experimental investigation of its thermoelectric (TE) properties as a potential filler atom in the CoSb₃-based skutterudite structure. In addition, reports on skutterudite compounds suggest enhancement in TE properties can occur when the filling fraction limit (FFL) is exceeded resulting in in situ secondary phases developing during synthesis. The results reported herein confirm important new concepts due to the multi-role chemistry of the Pr added Co₄Sb₁₂ skutterudites (i.e. Pr_yCo₄Sb₁₂), including: (1) exotic behavior in the Seebeck coefficient, α, as Pr is introduced to the matrix (2) an increase in ZT_max (≈1.0 at T ≈ 800 K) and the temperature range for ZT_max as Pr is increased and (3) confirmation of secondary phase(s) aiding in the improvement of TE properties.