The effect of light rare earth element substitution in Yb14MnSb11 on thermoelectric propertiesElectronic supplementary information (ESI) available: PXRD patterns of Yb14−pREpMnSb11 (RE = Pr and Sm, p = 0.2, 0.4, 0.6, 0.7, 0.8, 0.9, and 1.0), elemental maps, refined PXRD patterns of Yb13.82Pr0.18Mn1.01Sb10.99, Yb13.59Pr0.34Mn1.00Sb11.08, Yb13.53Pr0.45Mn1.02Sb10.99, Yb13.45Pr0.55Mn1.03Sb10.97, Yb13.80Sm0.19Mn1.00Sb11.02 and Yb13.50Sm0.53Mn1.06Sb10.89 before SPS and after measurement, and specific

• Main Authors: Hu, Yufei, Bux, Sabah K, Grebenkemper, Jason H, Kauzlarich, Susan M
• Format: Journal Article
• Language: English
• Published: 08.10.2015
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c5tc02326b

After the discovery of Yb 14 MnSb 11 as an outstanding p-type thermoelectric material for high temperatures (≥900 K), site substitution of other elements has been proven to be an effective method to further optimize the thermoelectric properties. Yb 14− x RE x MnSb 11 (RE = Pr and Sm, 0 < x < 0.55) compounds were prepared by powder metallurgy to study their thermoelectric properties. According to powder X-ray diffraction, these samples are iso-structural with Yb 14 MnSb 11 and when more than 5% RE is used in the synthesis the presence of (Yb,RE) 4 Sb 3 is apparent after synthesis. After consolidation and measurement, (Yb,RE)Sb and (Yb,RE) 11 Sb 10 appear in the powder X-ray diffraction patterns. Electron microprobe analysis results show that consolidated pellets have small (Yb,RE)Sb domains and that the maximum amount of RE in Yb 14− x RE x MnSb 11 is x = 0.55, however, (Yb,RE) 11 Sb 10 cannot be distinguished by electron microprobe analysis. By replacing Yb 2+ with RE 3+ , one extra electron is introduced into Yb 14 MnSb 11 and the carrier concentration is adjusted. Thermoelectric performance from room temperature to 1275 K was evaluated through transport and thermal conductivity measurements. The measurement shows that Seebeck coefficients initially increase and then remain stable and that electrical resistivity increases with substitutions. Thermal conductivity is slightly reduced. Substitution of Pr and Sm leads to enhanced zT . Yb 13.82 Pr 0.18 Mn 1.01 Sb 10.99 has the best maximum zT value of ∼1.2 at 1275 K, while Yb 13.80 Sm 0.19 Mn 1.00 Sb 11.02 has its maximum zT of ∼1.0 at 1275 K, respectively, ∼45% and ∼30% higher than Yb 14 MnSb 11 prepared in the same manner. The zT of Yb 14 MnSb 11 is improved by the introduction of a light rare earth element, RE 3+ (RE = Pr, Sm) with partially filled f-levels. The carrier concentration is reduced upon substituting RE 3+ for Yb 2+ , adding one electron to the system and improving the zT values 30-40% over that of the pristine material.