The competition between phase stability and band gap in Yb-filled cobalt-free Fe4-Ni Sb12 skutterudites

Abstract

We report the influence of Ni substituting for Fe on the phase stability and thermoelectric properties of Yb x Fe 4- y Ni y Sb 12 ( x = 0.6, 0.7, 0.8, 0.9, 1.0; y = 1.0, 0.8, 0.6). Ni substituting can efficiently enhance phase stability but reduces band gap, which establishes an optimum Ni substituting content to keep the balance. Meanwhile, the atomic disorder caused by Ni substituting together with Yb-filling leads to a significant reduction in lattice thermal conductivity. The most marked reduction in lattice thermal conductivity is achieved in the Yb 0.9 Fe 3.4 Ni 0.6 Sb 12 compound with a minimum value of 0.71 W m −1 K −1 at about 650 K. Finally, a peak zT of 0.85 is attained at 673 K in the Yb 0.9 Fe 3.4 Ni 0.6 Sb 12 compound, which is comparable to other p-type skutterudites at the same temperature. This work highlights the importance of considering the competition between phase stability and band gap when designing high thermoelectric performance cobalt-free skutterudites. • Importance of considering the competition between phase stability and band gap. • The atomic disorder reduces lattice thermal conductivity greatly for 0.71 W m −1 K −1 . • A maximum zT value of 0.85 is achieved in Yb 0.9 Fe 3.4 Ni 0.6 Sb 12 and YbFe 3.4 Ni 0.6 Sb 12 .