2019 APS March Meeting, Boston, MA - Oral (R47.00008)
Session R47: Thermoelectrics -- Characterization and Metrology, 9:48 AM–10:00 AM, Thursday, March 7, 2019
Title: NMR investigation of filled skutterudites BaxYbyCo4Sb12 and AxCo4Sb12 (A = Ba, Sr)
Abstract Body: Considered as one of the most promising thermoelectric families, skutterudite CoSb3 shows a high ZT value when prepared with filler atoms such as Ba, Sr, Yb, etc. We report Co NMR and transport measurements on BaxYbyCo4Sb12 and AxCo4Sb12 (A = Ba, Sr) as promising thermoelectric candidates. To analyze the experimental results, we developed a formalism for the NMR shifts and T1, allowing for arbitrary carrier densities rather than treating the extreme metallic or non-degenerate limit. We find that a model in which a large density of defect states located just below the conduction band edge dominate the electrical behavior works very well, providing a consistent picture of both the NMR and transport results. The carrier effective masses and g-factors estimated from NMR fitting results are in close agreement with each other. Additional contributions observed in shift and 1/T1 measurements are shown to correspond to the susceptibility of electrons in localized states.
Funding Acknowledgement: This work was supported by the Robert A. Welch Foundation, Grant No. A 1526. Synthesis of skutterudites samples at the University of Michigan was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DESC0000957.