Preparation And Thermoelectric Properties Of P-type Barium And Indium Double-filled Skutterudite Materials

Skutterudite is one of the promising thermoelectric (TE) materials in the moderate temperature range. How to prepare a p-type skutterudite material with comparable ZT value to that of n-type skutterudite material is still a research topic in the TE field. In this thesis, a series of Ba and In double-filled p-type skutterudite TE materials with nominal composition Ba0.3In0.2FeCo3Sb12-xGex (0-0.4,△x=0.1) have been prepared by traditional annealing and spark plasma sintering (SPS) methods. The effects of Ge dopant on the phase composition and TE properties of Ba0.3In0.2FeCo3Sb12-xGex were investigated. A rapid non-equilibrium technique employing melt-quenching and subsequent SPS has been developed to prepare filled skutterudite TE materials. The preparation time was remarkably reduced to less than30hours from over10days for traditional method. The effects of the SPS holding time and sintering temperature on the phase composition and TE properties of (Ba, In) double-filled skutterudites have been investigated.Phase composition and TE properties of Ba0.3In0.2FeCo3Sb12-xGex indicate that a single-phase skutterudite material was obtained in the samples with x<0.2, and trace Fe1.67Ge was detected in the samples with x≥0.3. The electrical conductivity increased and Seebeck coefficient decreased with increasing x in the range of0-0.2, while the inverse behaviors of electrical conductivity and Seebeck coefficient were observed in the samples with x≥0.3. The lattice thermal conductivity of all the Ge-doped samples was considerably reduced as compared to that of un-doped Ba0.3In0.2FeCo3Sb12, and the lowest value of lattice thermal conductivity of the Ba0.3In0.2FeCo3Sb11.8Ge0.2sample is only about1.0W·m-1·K-1at750K. The highest ZT value of0.54was obtained at800K for the Ba0.3In0.2FeCo3Sb11.7Ge0.3sample, increased by10%as compared to that of the Ba0.3In0.2FeCo3Sb12.Filled skutterudite materials with a trace of FeSb2、FeSb and InSb have been prepared by the new rapid non-equilibrium method. The electrical conductivity increased and then decreased with increasing SPS holding time, while the inverse behavior of Seebeck coefficient was observed. The largest power factor of2.46m W m-1·K-2was obtained at800K for the sample holding for15min. Increasing the holding time can effectively decrease the thermal conductivity and lattice thermal conductivity, the lowest thermal conductivity reached3.27W·m-1·K-1for the sample holding for20min. The enhanced ZT value can be obtained by using the optimization of holding time. The highest value of0.6, a comparable value to that of the sample prepared by traditional method, was obtained for the sample holding for15min.BaIno.5Fe3.7Coo.3Sb12materials, prepared by the rapid non-equilibrium technique, were composed of skutterudites and a trace of FeSb2, Sb and InSb. The electrical conductivity decreased slightly and the Seebeck coefficient increased with increasing the sintering temperature. The largest power factor of3.1m W m-1·K-2was obtained at800K for the sample with sintering temperature of798K. With increasing the sintering temperature, the thermal conductivity decreased slightly and then increased, while the lattice thermal conductivity increased gradually. The lowest thermal conductivity reached3.68W·m-1·K-1for the sample with the sintering temperature of798K. The enhanced ZT value can be obtained by using the optimization of sintering temperature, the highest value of0.68was obtained for the sample with sintering temperature of798K, increased by9.7%as compared with that of the sample with sintering temperature of773K.