Synthesis And Thermoelectric Properties Of P-type Filled Skutterudite Compounds With Nanostructure

The filled Skutterudite compounds attract much attention due to their high mobilities and relative large Seebeck coefficients in the medium temperature range of 600⁸00K. Their thermal conductivities are so high that how to decrease their lattice thermal conductivities and improve their ZT values becomes a research focus.In this research, simple phase p-type Ba_yFe_xCo_4-xSb₁₂ filled Skutterudite compound powder with average grain size 3μm was synthesized using a two-step solid-state reaction method. Nanostructure Ba_yFe_xCo_4-xSb₁₂ powder was prepared by high energy ball milling method. The influence of ball milling parameter(quality of ball and powder in ratio, velocity, time) on the average grain size was researched. In appropriate condition, powder with average grain size 100nm was prepared.Ba_yFe_xCo_4-xSb₁₂ bulk materials was prepared by spark plasma sintering(SPS) method using nanostructure powder as starting materials. The influence of sintering time and sintering temperature on the average grain size of the sinter was researched. It was showed that with the sintering temperature and sintering time increasing, average grain size of bulk materials grew evidently. Ba_yFe_xCo_4-xSb₁₂ bulk materials with average grain size 150nm was prepared in the condition :sintering time 5min, sintering temperature550℃.The thermal conductivity, electrical conductivity and Seebeck coefficient in samples with different average grain size were measured. The influence of nanostructure on the thermal conductivity, electrical conductivity and Seebeck coefficient was investigated. It was showed that nanostructure has a significant effect in Seebeck coefficient. Seebeck coefficient decreased in a large range. Second phase and grain size both have a momentous effect in lattice thermal conductivity. Electrical conductivity changed little.