Innovative synthesis of mesostructured CoSb3-based skutterudites by magnesioreduction

High purity CoSb3, Ni0.06Co0.94Sb3 and In0.13Co4Sb12 were synthesized from oxides by magnesioreduction. This novel synthesis route to CoSb3-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 CoSb3 and Ni0.06Co0.94Sb3 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 CoSb3, Ni0.06Co0.94Sb3 and In0.13Co4Sb12, 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. [Display omitted] •Magnesioreduction of oxides is used to prepare skutterudites.•Well-crystallized and submicronic powders are obtained at low temperature.•The mesostructuration survives after spark plasma sintering.•Accordingly, improved thermoelectric performances are achieved.•Thermoelectric properties are discussed toward microstructure of the materials.