Enhanced thermoelectric performance of N-type Bi2Te2.7Se0.3-based materials by superparamagnetic Fe3O4 nanoparticles

Abstract

Magnetic particles as second phases have been extensively reported to optimize electrical and thermal transport properties in single thermoelectric (TE) matrixes. However, the comparative performance of TE substrates with different carrier concentrations that incorporates magnetic particles are lacking from literature. In this work, a small amount of Ag2Se particles was employed as a second phase for the reduction of the electrical conductivity of Bi2Te2.7Se0.3 (BTS) by constructing n-type homojunction or doping effect, and then the BTS based thermoelectric performance was studied by incorporating single-phase superparamagnetic Fe3O4 nanoparticles. A series of BTS-xwt%Ag2Se-ywt%Fe3O4 TE ingots were sintered and their transport properties were investigated. Finally, the maximum recorded ZT values were 0.78 for BTS-0.4 wt%Ag2Se and 0.72 for BTS-0.4 wt%Fe3O4, which are 1.3 times and 1.2 times higher that of the pure sample respectively. For BTS-0.4 wt%Ag2Se-0.4 wt%Fe3O4, the maximum and average ZT values were 0.89 and 0.77, representing 48% and 40% increments compared with the pure sample. This study confirms the effectiveness of superparamagnetic Fe3O4 nanoparticles in the performance improvement of TE ingots with low electrical conductivity.