A New N-Type High Entropy Semiconductor AgBiPbSe2S with High Thermoelectric and Mechanical Properties
Exploring N-type High-entropy materials with both high thermoelectric and mechanical properties is highly desirable for all-high-entropy thermoelectric generators (TEGs) since the thermoelectric and mechanical properties of N-type one are largely behind its P-type counterparts. Herein, a new rock-salt structure N-type high entropy thermoelectric AgBiPbSe 2 S is introduced with a bandgap of ≈0.43 eV. The atomic radii difference of each component results in a large lattice distortion of 0.246, leading to a low thermal conductivity of 0.36 W m −1 K −1 at 823 K. The figure of merit ( ZT ) reaches 0.6 for AgBiPbSe 2 S at 823 K. Moreover, Ag 2 Se precipitates are included in AgBiPbSe 2 S to filter low energy carriers for high Seebeck coefficients and to scatter phonons with nanoscale wavelength for ultralow lattice thermal conductivities. Consequently, a peak ZT of ≈1.18 at 823 K and an average ZT of 0.60 at 400–823 K are obtained for Ag 1.02 BiPbSe 2 S. More importantly, high mechanical properties are also obtained in Ag 1.02 BiPbSe 2 S, of which the Vickers hardness and flexural strength are ≈209 Hv and 32 MPa, respectively, originating from the enhanced lattice friction by chemical short-range disorder (i.e., high entropy effect) and dispersion strengthening caused by Ag 2 Se nanoprecipitates.
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