Enhanced thermoelectric properties of Bi₂O₂Se by Bi₂Te_2.7Se_0.3 addition

In this work, the thermoelectric properties of Bi₂O₂Se by Bi₂Te_2.7Se_0.3 addition through liquid assisted shear exfoliation- restacking (LASE-R) process were studied. The results show that the Bi₂Te_2.7Se_0.3 can alloy with Bi₂O₂Se and reduce the band gap, which introduce more electrons and improve the electrical conductivity of Bi₂O₂Se. Moreover, Bi₂Te_2.7Se_0.3 addition act as a liquid phase sintering aids here, which can promote crystal growth and increase the sintering density of Bi₂O₂Se. Owing to the offset effect between |S| and σ, the absolute Seebeck coefficient |S| of all samples drops first and then rises with the increase of Bi₂Te_2.7Se_0.3 content. Thus, the power factor is effectively improved. In addition, the lattice thermal conductivity is also suppressed to the nearly minimum theoretical limit, which should be attributed to the enhanced phonon-scattering by alloying. Therefore, a high figure of merit of 0.7 at 772 K was achieved for Bi₂O₂Se- 0.3 mol% Bi₂Te_2.7Se_0.3.