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Reducing lattice thermal conductivity is one of the most effective routes for improving the performance of thermoelectric materials. Herein, a novel alloy design concept, i.e., the high-entropy alloy concept, is introduced as a new strategy to reduce lattice thermal conductivity and the BiSbTe 1.5 Se 1.5 high-entropy alloy was chosen as a paradigm to demonstrate the applicability of this new approach. It was found that the lattice thermal conductivity of this high-entropy alloy is quite low, i.e., $0.47 W m À1 K À1 at 400 K, which results from its severe lattice-distortion. In addition, the minor addition of Ag could improve the absolute value of its Seebeck coefficient and further reduce its lattice thermal conductivity.Consequently, a peak ZT value of 0.63 was observed at 450 K for this alloy with the addition of 0.9 at% Ag. Our current results suggest that the revolutionary alloy design concept is a promising strategy for developing novel thermoelectric materials with desirable properties.

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