Scientists improve thermoelectric performance of n-type transition metal selenide through nanoinclusions

A research team led by Prof. Qin Xiaoying from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has improved the thermoelectric performance of an n-type transition metal selenide, Bi₂Te_2.7Se_0.3 (BTS), by incorporating MnSb₂Se₄ (MSS) nanoinclusions. Results were published in two articles in the Chemical Engineering Journal.

Thermoelectric technology has received considerable attention as a potential solution to energy problems. However, the low thermoelectric value ZT (figure of merit) and energy conversion efficiency of N-type bismuth telluride currently limit its widespread commercial application. Nanoengineering is an effective way to improve the thermoelectric properties of materials, but selecting a suitable second phase can be challenging.

In this study, the researchers found that incorporating MnSb₂Se₄ into BTS can yield remarkable results.

Incorporated MSS nanoinclusions have been shown to have multiple benefits. It could simultaneously increase the power factor, resulting from the improved thermal performance due to the energy filtering effect and reduce lattice thermal conductivity originating from intensified phonon scattering by the dislocations.

The BTS/0.50wt%MSS composite sample demonstrated a maximum thermoelectric ZT of 1.23 at 345K, and an average ZT of 1.15 in the temperature range of 300–473K.

Notably, these values represented an approximate increase of 48% and 42%, respectively, over the matrix BTS. In addition, the composite sample exhibited improved mechanical properties, as evidenced by a 17% increase in its Vickers hardness.

The results indicate that the incorporation of the MnSb₂Se₄ secondary phase is an effective way to improve thermoelectric performance and mechanical properties of BTS.

The researchers have made significant progress in optimizing the thermoelectric properties of thermoelectric materials at room temperature. In 2022, they found that incorporating polyaniline nanoparticles into the BTS matrix could enhance phonon scattering and reduce the lattice thermal conductivity by 49% at 300K.

"It results in an 8% increase in power factor and a maximum ZTmax of 1.22 at 345K for the 1.5 wt% composite sample," said Chen Tao, a member of the team, "which is an attempt of organic compound, and also for the later inorganic-organic compound system research to lay a certain foundation."