Preparation and thermoelectric properties of micro-nanostructured Yb_0.3Co₄Sb₁₂

Yb-filled bulk CoSb₃ skutterudites were prepared by melting method combining with Spark Plasma Sintering (SPS). Bulk Yb_0.3Co₄Sb₁₂ compounds with superior thermoelectric properties (ZT=1.19, 800 K) were achieved at last. Then high-energy ball milling was employed to prepare nano-sized particles. After that, the nano-sized Yb_0.3Co₄Sb₁₂ particles were sintered by SPS apparatus to get bulk sample. Particle morphology and microstructure observation were performed by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). The thermoelectric properties of bulk materials were measured by ZEM-3 and LFA427. There were no decomposition and crystal form transition appeared after milling 10 h according to XRD patterns. The particle size decreased greatly according to FESEM and TEM observation and after sintering the grain size was ~500 nm and partly was less than 100 nm. Compared with the bulk without milling, the Seebeck coefficient after milling increased a little and thermal conductivity decreased 1/3. However, at the same time, the electrical conductivity decreased about 10 times so that the ZT of milled bulk Yb_0.3Co₄Sb₁₂ decreased.