Realizing phase segregation in the Ba0.2(Co1−xIrx)4Sb12 (x = 0, 0.1, 0.2) filled skutterudite system

Polycrystalline-filled skutterudite Ba0.2(Co1−xIrx)4Sb12 (x = 0, 0.1, 0.2) was synthesized by melting–quenching–annealing combined with a subsequent spark plasma sintering method. A solid solution of Ir was formed at the Co sites during the first annealing step (800 °C for 7 days), then Ir-rich nanocrystals with the composition Ba0.2(Co0.9Ir0.1)4Sb12 precipitated during the subsequent annealing period (550 °C for 30 days). This is the first time that phase segregation has been realized in this system. The correlation of the fabrication, microstructure and thermal transport properties is discussed.