Effect of rapid solidification on the synthesis and thermoelectric properties of Yb-filled Co4Sb12 skutterudite

In this work the effect of different processing routes on the kinetics of formation of Co4Sb12 phase and Yb filling in the skutterudite cage, as well as thermoelectric behaviour was evaluated. As prepared slowly cooled ingot and rapidly solidified ribbons show the presence of multiple phases, as a consequence of the complex solidification path characterized by two peritectic reactions. As solidification rate increases, grain refinement is promoted. Annealing of rapidly solidified ribbons induces a faster solubilisation of Yb due to increased grain boundary diffusivity. For this reason, rapid solidification can be considered a promising intermediate step for lowering the total processing time of skutterudites. Sintering of powders obtained from the slowly cooled ingot and rapidly solidified ribbons leads to the formation of massive samples with different densities, depending on the particle size distributions of the starting powders. The effect of Yb content on the thermoelectric properties was critically analysed, considering both data from the literature and this work.