Theoretical Maximum Thermoelectric Performance of Cu-doped and Electric Current Pulse-treated Bi-Sb-Te Alloys

Abstract

Bi₂Te₃ shows high thermoelectric performance near room temperature, making it the most widely used material in thermoelectric cooling applications. Cu doping has been found to be effective in improving the thermoelectric performance of Bi₂Te₃. However, due to the problem of easy migration of Cu ions, the stability of Cu-doped Bi₂Te₃ is always an issue, and therefore worth exploring. This study utilizes the Single Parabolic Band (SPB) model to analyze the electronic transport properties of Cu_<i>x</i>Bi_0.3Sb_1.7-<i>x</i>Te₃. We investigate how electronic band parameters (effective mass, non-degenerate mobility, weighted mobility, and <i>B</i>-factor) evolve with increasing Cu content (<i>x</i>). Additionally, the influence of electric current pulse (ECP) treatment is examined. Experimentally, the <i>zT</i> of <i>x</i> = 0.001 was higher than <i>x</i> = 0.0025 samples near room temperature. However, the SPB model predicts that due the higher <i>B</i>-factor of the <i>x</i> = 0.0025 sample, its theoretical maximum <i>zT</i> can be as high as ~1.48 at 350 K. Based on literature data on thermoelectric transport properties in the <i>x</i> = 0.001 sample after the ECP treatment, the impact of the ECP treatment on the electronic band parameters and the lattice thermal conductivity of the <i>x</i> = 0.0025 sample is estimated. ECP treatment slightly reduces electrical performance below 350 K, but it significantly suppresses the lattice thermal conductivity, ultimately leading to an enhanced <i>zT</i>. The predicted maximum <i>zT</i> reaches ~1.54 at 300 K.