Innovative synthesis of mesostructured CoSb 3 -based skutterudites by magnesioreduction

High purity CoSb 3 , Ni 0.06 Co 0.94 Sb 3 and In 0.13 Co 4 Sb 12 were synthesized from oxides by magnesioreduction. This novel synthesis route to CoSb 3 -based skutterudites directly yields highly crystalline powders with submicronic grain size. Densified mesostructured pellets with an average grain size ranging between 550 and 800 nm were obtained by spark plasma sintering. The strong phonon scattering induced by the mesostructuration leads to a lattice thermal conductivity reduction up to 25% for CoSb 3 and Ni 0.06 Co 0.94 Sb 3 at 300 K without significantly degrading the electronic properties. Consequently, maximum ZT figures-of-merit of 0.09, 0.60 and 0.75 are found for CoSb 3 , Ni 0.06 Co 0.94 Sb 3 and In 0.13 Co 4 Sb 12 , respectively, showing the ability of this scalable process to reach the best performances reported in literature for these compositions at moderate temperature and annealing duration.