Reducing Lattice Thermal Conductivity of the Thermoelectric Compound AgSbTe2 (P4/mmm) by Lanthanum Substitution: Computational and Experimental Approaches |
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Authors: | Yaron Amouyal |
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Affiliation: | 1. Department of Materials Science and Engineering, Technion - Israel Institute of Technology, 32000, Haifa, Israel
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Abstract: | In this study we performed lattice dynamics first-principles calculations for the promising thermoelectric (TE) compound AgSbTe2, and estimated the stability of its three polymorphs over a wide temperature range from 0 to 600 K. We calculated the vibrational density of states of the AgSbTe2 (P4/mmm) phase. The results suggested that formation of substitutional defects at Ag-sublattice sites impedes lattice vibrations, thereby reducing lattice thermal conductivity. We focused on calculations based on the Debye approximation for the compound La0.125Ag0.875SbTe2, and predicted reduction of the average sound velocity from 1684 to 1563 m s?1 as a result of La doping. This is manifested as a ca. 14% reduction in thermal conductivity. To confirm the results from computation we produced two Ag–Sb–Te-based alloys, a ternary alloy without La addition and a quaternary alloy containing La. We measured the thermal conductivity of both alloys by use of the laser flash analysis method, and, as a result of La alloying, observed a reduction in thermal conductivity from 0.92 to 0.71 W m?1 K?1 at 573 K, as calculated from first principles. |
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