High thermoelectric figure of merit in well optimized YbyCo4Sb12. Issue 47 (12th November 2020)

• Record Type: Journal Article
• Authors: Alleno, E.; Benyahia, M.; Vaney, J. B.; Provost, K.; Paul-Boncour, V.; Monnier, J.; Dauscher, A.; Lenoir, B.
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 47(2020)
• Page Start: 17034
• Page End: 17044
• Publication Date: 2020-11-12
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc03455j
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : By carefully controlling the ytterbium concentration, the power factor has been optimized for Yb y Co4 Sb12, leading to ZT = 1.4 at 750 K in Yb0.15 Co4 Sb12 . Abstract : By implementing X-ray absorption spectroscopy among other techniques, ytterbium was inferred to display a valence of 2 in the thermoelectric Yb y Co4 Sb12 skutterudites (0.10 ≤ y ≤ 0.20). Consequently, the correlation PF(A 3+ ) < PF(A 2+ ) < PF(A 1+ ) between the valence of the filler atom and the power factor (PF) could be established in a generic set of A y Co4 Sb12 skutterudites (A = filler atom and electron donor). By grinding the Yb y Co4 Sb12 samples under inert atmosphere prior to densification by Spark Plasma Sintering, no spurious oxidation of Yb occurred, conversely to what happens when grinding in air. This led to the effective ytterbium concentration being strictly equal to the nominal one, up to the solubility limit determined to be y lim = 0.41 ± 0.02 mol per formula unit when the Yb y Co4 Sb12 compounds are synthesized at 1073 K. The maximum PF = 4.2 mW m −1 K −2 at 300 K is reached in Yb0.15 Co4 Sb12, for the first time at the theoretically predicted electron concentration n opt = 1.8 ± 0.2 × 10 20 cm −3, thus evidencing the optimization of this compound. Finally, Yb0.15 Co4 Sb12 also displays the best thermoelectric properties in the series, with a figure of merit ZT max = 1.4 and PF = 5.5 mW m −1 K −2 at 750 K.