Band Structure Engineering and Thermoelectric Properties of Charge-Compensated Filled

1 Supplementary information

2Band Structure Engineering and Thermoelectric Properties of Charge-Compensated Filled

3 Skutterudites

4 Xiaoya Shi1, Jiong Yang2, Lijun Wu1, a, James R. Salvador3, b, Cheng Zhang1, William L. 5 Villaire4, Daad Haddad3, Jihui Yang2, Yimei Zhu1, and Qiang Li1, c

6 1 Condensed Matter Physics and Materials Science Department, 7 Brookhaven National Laboratory, Upton, New York 11973, USA

8 2 Materials Science & Engineering Department 9 University of Washington, Seattle, WA 98195, USA

10 3 Chemical and Materials Systems Lab 11 General Motors R&D Center, Warren, MI 48090, USA

12 4 Fuel Systems Engineering 13 General Motor Global Design, Engineering and Product Programs 14 Warren, MI 48090-9020 15 Nominal Composition EMPA Composition Lattice parameter (Å)

Ga0.20Co4Sb11.9333 9.0393 Yb0.05 Ga0.20Co4Sb11.9333 9.0414 Yb0.10 Ga0.20Co4Sb11.9333 9.0435 Yb0.15 Ga0.20Co4Sb11.9333 9.0463 Yb0.20 Ga0.20Co4Sb11.9333 9.0494 Yb0.26 Ga0.20Co4Sb11.9333 Yb0.24 Ga0.15Co4Sb11.87 9.0527 Yb0.20 Co4Sb12 Yb0.18 Co4Sb11.71 9.0523

Yb0.20 Ga0.10Co4Sb11.9666 Yb0.18 Ga0.08Co4Sb11.63 9.0499 Yb0.20 Ga0.15Co4Sb11.95 Yb0.18 Ga0.13Co4Sb11.65 9.0498 Yb0.25 Ga0.15Co4Sb11.95 Yb0.23 Ga0.14Co4Sb11.50 9.0493 Yb0.30 Ga0.15Co4Sb11.95 Yb0.29 Ga0.14Co4Sb11.50 9.0525 Yb0.35 Ga0.15Co4Sb11.95 Yb0.31 Ga0.14Co4Sb11.53 9.0553 Yb0.40 Ga0.15Co4Sb11.95 Yb0.38 Ga0.14Co4Sb11.47 9.0592

16 Supplementary Table 1. Nominal composition, EMPA composition and lattice

17parameters. Samples are YbxGa0.2Co4Sb11.9333 (x = 0, 0.05, 0.10, 0.15, 0.20, 0.26),

18YbyGa0.15Co4Sb11.95 (y = 0.25, 0.30, 0.35, 0.40) and Yb0.20GazCo4Sb12-z/3 (z = 0, 0.10, 0.15) at room

19temperature for all the samples.

20 21 22Supplementary Figure 1. EPMA mapping results of the sample Yb0.30Ga0.15Co4Sb11.95. With

23the exception of Yb the maps above are very uniform indicating a homogenous distribution of

24the elements with very little to no oxide content. EPMA also finds that all four constituent

25elements are present in each grain.

26 27Supplementary Figure 2. First-principles band structure calculations. The left is

28Ga0.25Co4Sb12 and the right is In0.25Co4Sb12, assuming the IIIA atoms are all at filler sites. The zero

29energy points represent the Fermi levels (EFs) of the two compounds.