TY  - JOUR
A1  - Ryll, Britta
A1  - Schmitz, Andreas
A1  - de Boor, Johannes
A1  - Franz, Alexandra
A1  - Whitfield, Pamela S.
A1  - Reehuis, Manfred
A1  - Hoser, Andreas
A1  - Müller, Eckhard
A1  - Habicht, Klaus
A1  - Fritscht, Katharina
T1  - Structure, phase composition, and thermoelectric properties of YbxCo4Sb12 and their dependence on synthesis method
JF  - ACS applied energy materials
N2  - We present a combined microscopic and macroscopic study of YbxCo4Sb12 skutterudites for a range of nominal filling fractions, 0.15 < x < 0.75. The samples were synthesized using two different methods — a melt–quench–annealing route in evacuated quartz ampoules and a non-equilibrium ball-mill route — for which we directly compare the crystal structure and phase composition as well as the thermoelectric properties. Rietveld refinements of high-quality neutron powder diffraction data reveal about a 30–40% smaller Yb occupancy on the crystallographic 2a site than nominally expected for both synthesis routes. We observe a maximum filling fraction of at least 0.439(7) for a sample synthesized by the ball-mill routine, exceeding theoretical predictions of the filling fraction limit of 0.2–0.3. A single secondary phase of CoSb2 is observed in ball-mill-synthesized samples, while two secondary phases, CoSb2 and YbSb2, are detected for samples prepared by the ampoule route. A detrimental influence of the secondary phases on the thermoelectric properties is observed for secondary-phase fractions larger than 8 wt % regardless of the kind of secondary phase. The largest figure of merit of all samples with a ZT ∼ 1.0 at 723 K is observed for the sample with a refined Yb content of x2a = 0.159(3), synthesized by the ampoule route.
KW  - thermoelectric materials
KW  - skutterudite
KW  - melt-quench-anneal
KW  - ball mill
KW  - neutron powder diffraction
KW  - thermoelectric properties
KW  - figure of merit
Y1  - 2017
U6  - https://doi.org/10.1021/acsaem.7b00015
SN  - 2574-0962
VL  - 1
IS  - 1
SP  - 113
EP  - 122
PB  - American Chemical Society
CY  - Washington
ER  -