Enhancing room temperature thermoelectric performance of n-type polycrystalline bismuth-telluride-based alloys via Ag doping and hot deformation

Abstract

Bismuth-telluride-based alloys are the unique thermoelectric materials for state-solid refrigeration around room temperature. For n-type polycrystalline counterparts, maximum figure of merit zTs are often shifted above 400 K due to the increased carrier concentration induced by the donor-like effect during the pulverization of ingots. Herein, we report a synergistic optimization procedure, combining Ag doping with hot deformation, to boost room temperature thermoelectric performance of n-type polycrystalline Bi2Te2.7Se0.3 alloys. The Ag doping optimizes the carrier concentration, contributing to an improved power factor and a reduced electrical thermal conductivity. The hot deformation process improves the carrier mobility due to the enhanced texture. As a consequence, a zT value of 1.0 at 300 K and a peak zT of 1.1 at 350 K are obtained in the twice hot deformed Ag0.011Bi2Te2.7Se0.3 alloy, which makes the n-type polycrystalline Bi2(Te,Se)3 alloys more suitable for solid-state refrigeration near room temperature.