Rapid preparation of bulk Al_xYb_0.25Co₄Sb₁₂ (x = 0, 0.1, 0.2, 0.3) skutterudite thermoelectric materials with high figure of merit ZT = 1.36

In this work, a skutterudite-based compound, Yb_0.25Co₄Sb₁₂, added with Al_x (x = 0, 0.1, 0.2, 0.3) was synthesized with a simple mechanical alloying technique followed by spark plasma sintering. The microstructural properties and thermoelectric properties of the as-sintered samples were investigated. The Al atoms formed AlSb nano-inclusions in the grain boundaries instead of entering the Sb-icosahedral voids, introducing point defects in the matrix lattice. By scattering low-energy electrons, the grain boundaries acted as a potential barrier in simultaneously attaining low electrical resistivity and high Seebeck coefficient. Therefore, Al_0.1Yb_0.25Co₄Sb₁₂ exhibited a high power factor of 4.8 × 10⁻³ W/m K² at 377 °C. AlSb of nanometer length enhanced interfacial phonon scattering, thereby significantly reducing the lattice thermal conductivity of Al_0.3Yb_0.25Co₄Sb₁₂ to 0.6 W/m K at 500 K. The Al_0.3Yb_0.25Co₄Sb₁₂ composite exhibited the highest figure of merit, ZT = 1.36, at 850 K.