Thermoelectric and mechanical properties on misch metal filled p-type skutterudites Mm0.9Fe4−xCoxSb12

Most of the recent work focused on improving the dimensionless figure-of-merit, ZT, of p-type skutterudites uses one or two fillers to tune the electrical and thermal properties. Considering the fact that the different fillers with varying atomic mass and ionic radii can vibrate with different amplitudes to scatter phonons of different mean free paths, we synthesized misch metal filled p-type skutterudites Mm0.9Fe4−xCoxSb12 (where Mm is La0.25Ce0.5Pr0.05Nd0.15Fe0.03, called misch metal). The samples were synthesized by hot pressing nano-powder made by ball milling the annealed ingot of Mm0.9Fe4−xCoxSb12 with varying concentration of cobalt, x. By tuning the Fe/Co ratio, we achieved a thermal conductivity of ∼2 W m−1 K−1 at room temperature and ∼2.3 W m−1 K−1 at about 530 °C and a power factor of ∼30 μW cm−1 K−2 at about 425 °C in Mm0.9Fe3.1Co0.9Sb12, leading to a peak ZT ∼1.1 at about 425 °C. The nano-indentation experiment reveals that hardness and elastic modulus of the material is about 4.2 GPa and 116 GPa, respectively.