Enhancement of High-Temperature Thermoelectric Properties in Pd-decorated Bi-Sb-Te System

Bismuth antimony telluride (Bi-Sb-Te)-based alloys remain the dominant choice for near-room-temperature thermoelectric cooling applications. One of the most studied approaches to improve the thermoelectric performance of Bi-Sb-Te alloys has been a nanostructuring strategy, to suppress the lattice thermal conductivity. This study investigates the impact of incorporating reduced pyrolyzed Pd acetate within a Bi_0.5Sb_1.5Te₃ matrix, building upon recent advancements in nanostructured Bi-Sb-Te alloys. While Pd acetate addition lowers the thermoelectric figure-of-merit (zT) at low temperatures, due to a corresponding increase in carrier concentration, it significantly enhances zT at higher temperatures. Notably, at 473 K, the addition of 0.02 wt.% Pd acetate increased zT by 32% (from 0.41 to 0.54) compared to the pristine sample. Above 423 K, the average zT improved by approximately 21% (from 0.44 to 0.53) in the 0.02 wt.% Pd acetate sample, primarily due to reduced bipolar conduction. Effective Mass (EM) modeling was employed to analyze band parameters. With the addition of Pd acetate, the density-of-states effective mass (m_d^*) generally increased, while non-degenerate mobility (µ₀) decreased. At 473 K, the thermoelectric quality factor increased by 42% (from 0.125 to 0.177) with 0.02 wt.% Pd acetate addition, indicating an improved theoretical maximum zT. These findings demonstrate the potential of incorporating Pd acetate for enhancing high-temperature thermoelectric performance in Bi_0.5Sb_1.5Te₃