High-temperature thermoelectric properties of p-type skutterudites Ba0.15Yb x Co3FeSb12 and Yb y Co3FeSb9As3

Abstract

Two series of p-type polycrystalline skutterudites, Ba 0.15 Yb x Co 3 FeSb 12 and Yb y Co 3 FeSb 9 As 3 with varying Yb concentrations, were synthesized by solid-state reaction and then densified by hot pressing. The phase and stoichiometries of the resulting materials were characterized by powder X-ray diffraction and energy dispersive spectroscopy, while their high-temperature transport properties were investigated from 300 to 800 K. The Seebeck coefficients and electrical resistivities increased linearly with increasing temperature for the double-filled specimens. The Seebeck coefficients and electrical resistivities did not change very much for the As-substituted specimens. The thermal conductivity for all specimens decreased with increasing temperature up to 700 K, corresponding to the plateau in the Seebeck coefficient, and then increased again due to bipolar diffusion. We find that double filling is a more feasible approach to thermoelectric property optimization than single filling with As substitution.

High Temperature Transport Properties of Yb and In Double-Filled p-Type Skutterudites

“…13 In 0.02 Co 3 FeSb 12 and Yb 0.39 In 0.02 Co 2.4 Fe 1.6 Sb 12 , respectively, with an increase in lattice parameter with Yb and In filling fractions and Co-to-Fe ratio, in agreement with previously reported data. Furthermore, the Yb filling fraction increases from 33% to 49% with increased Fe substitution, similarly reported for Gd and (Ba, Yb) filled skutterudites [10][11][12][13][14][15][16][17]. Elemental mapping from EDS data shows an even dispersion of elements for both specimens, indicating good homogeneity of the specimens, and corroborate our refinement results.…”

“…Yb) filled skutterudites [10][11][12][13][14][15][16][17]. Elemental mapping from EDS data shows an even dispersion of elements for both specimens, indicating good homogeneity of the specimens, and corroborate our refinement results.…”

“…The high-purity elements were weighed and loaded into silica crucibles in a N 2 for this study, which were chosen based off of previous studies of Yb single-filled Fe substituted skutterudites [11,12]. The specimens were sealed in a quartz tube under vacuum and reacted in a furnace at 1173 K for 48 h. The tube was removed and allowed to cool to room temperature in air before the specimens were ground into fine powders in a N 2 glove box and cold pressed into pellets.…”

“…Table 1 indicates the refinement results. The crystal structures were refined with space group Im3 (#204), and the initial atomic positions were based on data from previously reported Yb filled skutterudites [11,12]. The filler Yb atoms at the 2a site occupy less than the nominal composition, due in part to a trace amount of Yb 2 O 3 (observed in profiles at 29.7 • ) and to steric effects [11,12,15,16].…”

High Pressure Synthesis of p-Type CeyFe4−xCoxSb12 Skutterudites

“…Various approaches have been taken to improve the thermoelectric properties of skutterudites, such as void filling [4,5,6,7,8,9,10,11,12] and lattice atom substituting [13,14,15,16,17,18,19]. Compared with n-type CoSb 3 -based skutterudites for which ZT records are constantly refreshed [4,5,6], the developments in p-type skutterudites relatively lag behind [9,10].…”