Realizing High Thermoelectric Performance in Sb-Doped Ag₂Te Compounds with a Low-Temperature Monoclinic Structure

To recover the low-grade waste heat (300-500 K), it is of urgent importance to develop and improve the thermoelectric performance at a low-temperature region. Herein, we have realized a record high ZT value of 1.4 at 410 K and a record high average ZT value of 0.6 in the temperature interval from 300 to 400 K for Sb-doped Ag₂SbTe_1- (x = 0-0.03) compounds, which show an improvement of 180 and 120% compared to pristine Ag₂Te, respectively. Sb doping increases the carrier concentration and electrical conductivity, leading to a remarkable improvement of electrical transport properties. The Ag₂Sb_0.015Te_0.985 sample obtains the maximal power factor of 1.07 × 10^-3 W m^-1 K^-2 at 410 K, which is increased by 80% in comparison to that of pristine Ag₂Te. Moreover, as a result of the intensified alloying phonon scattering by Sb doping, Ag₂Sb_0.01Te_0.99 possesses the minimum lattice thermal conductivity of 0.35 W m^-1 K^-1 at 300 K, which demonstrates a decline of 57% compared to that of pristine Ag₂Te. All of these produce a great enhancement on the thermoelectric performance of Ag₂Te materials, which shows great potential in the application of recycling the low-grade waste heat at a low-temperature region.