High temperature thermoelectric properties of p-type skutterudites BaxYbyCo4-zFezSb12

Abstract

Several polycrystalline p-type skutterudites with compositions BaxYbyCo4−zFezSb12, with varying filler concentrations x and y, and z = 1 to 2, were synthesized by reacting the constituents and subsequent solid state annealing, followed by densification by hot-pressing. Their thermoelectric properties were evaluated from 300 to 820 K. The Yb filling fraction increased with Fe content while the amount of Fe substitution had little influence on the Ba filling fraction. High purity specimens were obtained when the Fe content was low. Bipolar conduction contributed to the thermal conductivity at elevated temperatures. A maximum ZT value of 0.7 was obtained at 750 K for the specimen with the highest Fe content and filling fraction. The potential for thermoelectric applications is also discussed.

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

“…The S and q values vary with total filling fractions for the double-filled specimens, and do not change very much with As substitution even with varying Yb content. The S and q values increase and decrease, respectively, with increasing total filling fraction for the double-filled compositions, as expected since a higher filler concentration results in a lower hole concentration, although the slightly different Co-to-Fe ratio would also affects the electrical properties [11,19]. The As-substituted compositions have larger q values than that of the double-filled compositions.…”

“…The small hole effective mass for p-type skutterudites, as compared to the much larger electron effective mass in n-type compounds, makes optimization of the thermoelectric properties of ptype skutterudite compounds much more challenging [5,6,23]. Although Fe substitution for Co strongly affects the transport properties and maximum filling fraction [19,24], Fe can be employed as a p-type dopant in filled skutterudites.…”

“…Thus far, n-type skutterudites have been widely investigated, resulting in relatively high ZT values from single, double, and triple atom filling [5,6,9]. Since both p-and n-type materials are essential for thermoelectric modules, enhancing the thermoelectric properties of p-type skutterudites are the current focus [10][11][12][13][14][15][16][17][18][19][20][21][22]. The small hole effective mass for p-type skutterudites, as compared to the much larger electron effective mass in n-type compounds, makes optimization of the thermoelectric properties of ptype skutterudite compounds much more challenging [5,6,23].…”

High‐temperature thermoelectric properties of p‐type skutterudites Ybx Co3FeSb12

“…In addition, the ionic radius and mass of Yb are smaller and heavier, respectively, than most other rare‐earth metals thus creating relatively strong phonon scattering centers 3, 4, 6. Since Fe has one less 3d electron than Co, and easily forms solid solutions with Co 4, Fe is a good candidate for p‐type filled skutterudites, although the Fe content strongly affects the transport properties and the Yb filling fraction 11, 12. It is therefore of interest to investigate Yb‐filled Fe‐doped p‐type skutterudites, with relatively low Yb concentrations for reasons that will be described below.…”

The Enhanced Thermoelectric Properties of Ba0.4Co4Sb11.7Te0.3 Prepared by the High-Pressure and High-Temperature Method

“…The minimum value 2.057 W · m -1 · K -1 was obtained at 743 K. The maximum ZT value of 0.87 was obtained for Ba 0.4 Co 4 Sb 11.7 Te 0.3 at temperature of 743 K, which is much higher than that of Co 4 Sb 11.7 Te 0.3 (0.34) and also higher than the result of G.S. Nolas (0.7) [21]. In summary, we conclude that The Ba atoms-filled in skutterudite can markedly increase the Seebeck coefficients, significantly reduce the thermal conductivity, almost do not change the electrical conductivity, and consequently greatly improve the ZT.…”