Highly Enhanced Average ZT in Bismuth Telluride Alloys via Pseudo Grain Boundary Engineering
Bismuth telluride (Bi2Te3)-based alloys remain the benchmark for low-temperature thermoelectric applications, yet their conversion efficiency is limited by the trade-off between electrical and thermal transport. This study introduces a pseudo grain boundary engineering strategy to simultaneously enhance the average figure of merit (ZT) in p-type (Bi,Sb)2Te3 (BST) materials. By incorporating Ag-based compounds, the carrier concentration is optimized via substitution of Ag+ ions, while the introduction of secondary phases at grain boundaries effectively suppresses lattice thermal conductivity. The approach yields a peak ZT of 1.35 at 393 K and an average ZT of 1.25 across 303–483 K, representing a significant improvement over pristine BST. Compared to prior reports, this work achieves superior average ZT while maintaining high electrical conductivity, addressing the longstanding bottleneck of thermal conductivity reduction without compromising carrier mobility. The findings underscore the efficacy of pseudo grain boundary engineering in advancing Bi2Te3-based thermoelectrics for solid-state cooling and power generation.