Enhanced near-room temperature thermoelectric performance and mechanical strength of n-type BiTeSe materials incorporated with Ag2Se inclusions

Abstract

Bi₂Te₃-based alloys are the best thermoelectric materials near room temperature. However, the lower thermoelectric (TE) performance of n-type Bi₂Te₃-based materials compared to their p-type ones seriously limits the conversion efficiency of thermoelectric devices. In this work, a Bi₂Te_2.5Se_0.5 matrix dispersed with Ag₂Se nanoparticles is fabricated. The anisotropic thermoelectric properties of the samples are investigated. A significant increase in electron mobility owing to highly-mobile Ag ions (Ag⁺) and an increased Seebeck coefficient due to optimized carrier concentration are achieved. Besides, the introduction of Ag₂Se nanoparticles results in lowered thermal conductivity due to reduced carrier concentration and enhanced phonon scattering between nanoparticles and phase/grain boundaries. As a result, substantial enhancement of the thermoelectric figure of merit ZT is obtained in both measured directions. In particular, the maximum ZT is 1.12 at 345 K and the average ZT is 1.06 at the measured temperature for the sample BTS-0.15vol%Ag₂Se, which is ∼62% and ∼63% larger than those of the pristine sample, respectively. Moreover, the compression strength of BTS-0.15vol%Ag₂Se is four fold as high as that of a commercial BTS sample. The results demonstrate that our work is an effective strategy for enhancing the TE performance and mechanical properties of n-type Bi₂Te₃-based materials.