Enhanced Thermoelectric Performance of Bi_0.5Sb_1.5Te₃ through Precise Pb Doping: Analysis Using the Single Parabolic Band Model

This study investigates the thermoelectric properties of Pb-doped p-type Bi_0.5Sb_1.5Te₃ alloys using the Single Parabolic Band (SPB) model, focusing on optimizing room-temperature performance. We systematically analyze the effects of Pb doping (0, 0.49, 0.65, 0.81, 0.97, and 1.3 at%) on key parameters including density-of-states effective mass (m_d^*), non-degenerate mobility (μ₀), weighted mobility (μ_W), and the thermoelectric quality factor (B-factor) at 323 K. The results reveal that m_d^* reaches a maximum of 1.37 m_e at 0.97 at% Pb doping, representing a 22.25 % increase over the pristine sample. The highest μ0 of 234.5 cm² V^-1 s^-1 is achieved at 0.65 at% Pb, highlighting the complex relationship between doping and carrier mobility. Notably, 0.97 at% Pb doping optimizes thermoelectric performance, yielding the highest μ_W, power factor, and B-factor. This composition also minimizes lattice thermal conductivity (κ_l) by 44.93 % compared to the undoped sample, significantly reducing phonon heat conduction. The Callaway-von Baeyer model corroborates these findings, indicating maximized point defect scattering at 0.97 at% Pb. A theoretical peak figure-of-merit (zT) of 1.74 is thus predicted at this doping level, demonstrating a possible substantial enhancement in thermoelectric efficiency upon appropriate carrier concentration tuning. The observed trends in Seebeck coefficient, Hall carrier concentration, and Hall mobility with increasing Pb content provide insights into the underlying mechanisms of performance enhancement. This comprehensive study highlights the critical role of precise Pb doping in optimizing the thermoelectric properties of Bi_0.5Sb_1.5Te₃ alloys for room-temperature applications and establishes a framework for future investigations into similar material systems.