High-pressure synthesis and excellent thermoelectric performance of Ni/BiTeSe magnetic nanocomposites

Abstract

The thermoelectric performance of BiTeSe alloys is very difficult to be enhanced using conventional approaches. Herein, a low-temperature and high-pressure sintering method was successfully developed to incorporate superparamagnetic Ni nanoparticles (Ni-NPs) into the Bi₂Te_2.7Se_0.3 matrix while suppressing deleterious chemical reactions at the Ni/Bi₂Te_2.7Se_0.3 heterointerface. The dimensionless thermoelectric figure of merit of Ni/Bi₂Te_2.7Se_0.3 nanocomposites is about 1.1 at 360 K, a remarkable 32% increase compared to the Bi₂Te_2.7Se_0.3 matrix. The cooling temperature difference of the single-leg device made with the nanocomposite reaches 4.2 K near room temperature, while it is only 2.6 K for the device made with the Bi₂Te_2.7Se_0.3 matrix. The excellent thermoelectric performance of the nanocomposite is attributed to its increased electrical conductivity due to charge transfer from Ni-NPs to the matrix, enhanced Seebeck coefficient from electron multiple scattering, and decreased lattice thermal conductivity from phonon scattering at the heterointerface. This work demonstrates that superparamagnetic metal nanoinclusions can enhance the thermoelectric and cooling performance of n-type BiTeSe alloys.