High-Pressure Synthesis of Te–Ge Double-Substituted Skutterudite with Enhanced Thermoelectric Properties

We synthesized Co 4 Sb 11 Te x Ge 1– x ( x = 0.5–0.8) using high-pressure, high-temperature conditions at ∼2 GPa and ∼900 K. The microstructure, morphology, and components were characterized via X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction (EBSD). EBSD indicated that the average grain size of Co 4 Sb 11 Te 0.8 Ge 0.2 was 1 μm. Electrical conductivity, Seebeck coefficient, and thermal conductivity were measured from 300 to 800 K. The minimum lattice thermal conductivity of Co 4 Sb 11 Te 0.8 Ge 0.2 was 0.72 W m –1 K –1, 74% lower than that at 300 K. The introduction of Te and Ge effectively enhanced point effects scattering and location scattering, notably decreasing lattice thermal conductivity. Therefore, the maximum zT value of Co 4 Sb 11 Te 0.8 Ge 0.2 was 1.13 at 800 K. These results indicate that high pressure combined with multielement substitution optimized the thermoelectric transport properties of skutterudites.