Highly Enhanced Average ZT in Bismuth Telluride Alloys via Pseudo Grain Boundary Engineering

• • Achieved peak ZT of 1.35 at 393 K and average ZT of 1.25 over 303–483 K, surpassing many prior BST studies (e.g., Sun et al.: ZT 1.42 at 373 K, avg 1.23; Qu et al.: ZT 1.35 at 393 K, avg 1.25). • • Ag-based compound incorporation raises carrier concentration via Ag+ substitution, enhancing electrical conductivity without degrading Seebeck coefficient. • • Pseudo grain boundary engineering introduces secondary phases that suppress lattice thermal conductivity, reducing total thermal conductivity while preserving carrier mobility. • • The strategy achieves a high average ZT across a broad temperature range (303–483 K), critical for practical device operation where temperature gradients vary.