Ultralow thermal conductivity and high thermoelectric figure of merit in Cu2Te-Ag2Te composites

Incorporation of nanostructures into bulk materials is an important strategy to enhance the thermoelectric figure of merit (zT). Herein, nanostructured Ag2Te (prepared by wet chemical synthesis) was mechanically alloyed with bulk Cu-2 Te (synthesized via melting route) to form composites of (Cu2Te)(100-x)-(Ag2Te), (where x varies from 0 to 50). The alloying increased the thermoelectric power factor from similar to 0.18 mW m(-1) K-2 (for pristine Cu2Te) to similar to 0.47 mW m(-1) K-2 for the composite at 588 K. The thermal conductivity reduced from similar to 3.5 W m(-1) K-1 in pristine Cu2Te to similar to 0.26 W m(-1) K-1 in the composites and reaches the theoretical minimum of Cu2Te (similar to 0.18 W m(-1) K-1) at high temperatures due to the additional scattering of carriers as well as phonons by the Ag2Te nanostructures. The combined effect of moderate power factor and ultralow thermal conductivity led to the high zT value of similar to 0.99 at 588 K in (Cu2Te)(50.00)-(Ag2Te)(50.00) that represents a significant improvement for Cu2Te based alloys. (C) 2020 Elsevier B.V. All rights reserved.