High Pressure Synthesis And Te Properties Of Ba-filling Type And Se Substituting Type Skutterudites Te Materials

Thermoelectric (TE) materials are a functional material which can convert heat and electricity directly. Over the past decade, Skutterudite (CoSb₃) materials have wide attention, due to relatively large carrier mobility and a high Seebeck coefficients and low electrical resistivity. However, Skutterudite materials also have a relatively high thermal conductivity, making it widely used and in commercial are greatly limited. In this study, High-pressure solid-state reaction method, systematic studies the influence of Ba filling and Se substitution CoSb₃ TE performance.Experiments using high purity powder of Co, Sb and Se as raw materials. Ba filled CoSb₃, using BaN₆ as the Ba source. Weighed according to the chemical formula (BaN₆)_xCo₄Sb₁₂ (x = 0.1～0.8) and Co₄Sb_12-xSe_x (x = 0.05～2) stoichiometric ratio of mixing respectively. Synthetic experiments using high-pressure solid-state reaction method, made in the different pressure synthesized samples. The samples phase identified by X-ray diffraction analysis, micro-crystal structure obtained by using SEM analysis. The samples TE properties measurement: resistivity using DC four-probe method, Seebeck coefficient through the self-made and corrected Seebeck coefficient tester. Some of Ba_xCo₄Sb₁₂ thermal conductivity tested.The analysis showed that: Polycrystalline samples of Ba_xCo₄Sb₁₂ and Co₄Sb_12-xSe_x have single Skutterudite phase synthesized by high-pressure solid state reaction method. The samples of Ba_xCo₄Sb₁₂ are N-type semiconductor, have fine grain structure and micron-level micro-pores. Its have very low thermal conductivity 1.25 W/(mK) for the sample Ba_0.372Co₄Sb₁₂ at 633K. The ZT values increases with the temperature increasing. The maximum ZT value of 1.01 obtained for Ba_0.372Co₄Sb₁₂ at 4.25GPa. Polycrystalline samples of Co₄Sb_12-xSe_x synthesized by High-pressure also have fine grain structure, with the concentration of Se increases, the samples semiconductor type from P-type into N-type. High Seebeck coefficient obtained for Co₄Sb_12-xSe_x. But electrical resistivities are also high for the samples. The maximum absolute value of Seebeck coefficient 501.59μV/K was obtained for the sample Co₄Sb_10.8Se_1.2. Sample Co₄Sb_11.9Se_0.1 have maximum power factor 3.77μW·cm^-1·K^-2.