Effects of Excess Sb on Thermoelectric Properties of Barium and Indium Double-Filled Iron-Based p-Type Skutterudite Materials
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A series of Ba and In double-filled iron-based p-type skutterudite thermoelectric (TE) materials with nominal composition BaInFe3.7Co0.3Sb12+m (0.72 ≤ m ≤ 2.4) have been prepared by melting, quenching, annealing, and spark plasma sintering (SPS) methods. The effects of excess Sb on the phase composition, microstructure, and TE transport properties of these materials were investigated in this work. All the SPS bulk materials are composed of the main skutterudite phase and trace InSb and FeSb2. The content of FeSb2 in the SPS bulk materials gradually decreased and that of InSb remained nearly invariable with increasing m. The impurities InSb and metallic Sb are found at grain boundaries. The amount of metallic Sb at grain boundaries gradually increased with increasing m. The excess Sb had no effect on the growth of grains. The dependence of the TE properties on m indicates that preventing the formation of FeSb2 by adjusting the excess Sb value may significantly improve the TE properties of Ba and In double-filled iron-based p-type skutterudite materials. The significant increases in the carrier concentration and electrical conductivity as well as the remarkable reduction in the lattice thermal conductivity of the sample with m = 0.96 are due to the significant reduction in the FeSb2 content induced by the excess Sb. The gradual increase in ZT with increasing m from 0.72 to 1.44 is attributed to the gradual decrease of the FeSb2 content, and the gradual decrease in ZT in the m range of 1.44 to 2.4 is due to the gradual increase of the Sb content in the Sb-In alloy impurity occurring at grain boundaries. The lowest lattice thermal conductivity of 0.31 W m−1 K−1 and the highest ZT value of 0.63 were obtained at 800 K for the sample with m = 1.44.
KeywordsFilled skutterudite Sb excess phase composition thermoelectric transport properties
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- 22.J.P. Fleurial, A. Borshchevsky, T. Caillat, D.T. Morelli, and G.P. Meisner, Proceeding of the 15th International Conference on Thermoelectrics (Pasadena, CA: IEEE, 1996), p. 91.Google Scholar