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

Abstract

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 Cu2Te (synthesized via melting route) to form composites of (Cu2Te)100-x–(Ag2Te)x (where x varies from 0 to 50). The alloying increased the thermoelectric power factor from ∼0.18 mW m−1K−2 (for pristine Cu2Te) to ∼0.47 mW m−1K−2 for the composite at 588 K. The thermal conductivity reduced from ∼3.5 W m−1 K−1 in pristine Cu2Te to ∼0.26 W m−1 K−1 in the composites and reaches the theoretical minimum of Cu2Te (∼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 ∼0.99 at 588 K in (Cu2Te)50.00–(Ag2Te)50.00 that represents a significant improvement for Cu2Te based alloys.