Enhanced Thermoelectric Performance of Nanostructured Nickel Doped Ag2Te

TL;DR

This study demonstrates that nickel doping and nanostructuring significantly enhance the thermoelectric performance of Ag2Te, achieving a maximum ZT of 0.86 near 480 K, surpassing previous reports.

Contribution

It introduces a combined approach of doping and nanostructuring to optimize thermoelectric properties of Ag2Te, achieving record-high ZT values.

Findings

Maximum ZT of 0.86 near 480 K in Ni-doped Ag2Te nanostructures

83% improvement over bulk Ag2Te thermoelectric performance

Structural phase transition influences thermal conductivity and thermoelectric efficiency

Abstract

We report on the thermoelectric properties of nickel doped Ag2-xNixTe (x = 0, 0.015, 0.025 & 0.055, 0.115, 0.155) nanostructures in the temperature (T) range of 5 K to 575 K. The electrical resistivity of Ag2Te nanostructure shows metallic behaviour in 5 K to 300 K initially that evolves into two metal to insulator transitions (MITs) at low and mid-temperature regimes with increasing x due to Mott-variable range hopping (VRH) and Arrhenius transports, respectively. Their Seebeck coefficient varies nearly in a linear fashion in this temperature range, showing metallic or doped-degenerate semiconducting behaviour. Notably, this behaviour of the Seebeck coefficient is in contrast to Mott VRH conduction as observed in resistivity. The steady increase in resistivity and S with the sharp decrease in thermal conductivity between 410 K to 425 K associated with the structural phase transition accomplishes a maximum thermoelectric figure of merit (ZT) of 0.86 near 480 K in x = 0.155. This is about 83 % more compared to that of bulk Ag2Te, and shows a significant improvement over the best value reported for Ag2Te nanostructures thus far. This study, therefore, shows that simultaneous nanocomposite formation, doping and nanostructuring could be an effective strategy for tuning the electron and phonon transports to improve the thermoelectric properties of a material.