Impact of Heavy, Large-Radius Metal Doping on the Performance of BiSbTe Compounds

Abstract In this study, the structural and transport properties of BiSbTe compounds doped with boron (B), barium (Ba), and ytterbium (Yb) via partial substitution of Bi atoms were systematically investigated. B-, Ba-, and Yb-doped Bi 2− x Te 3 and Sb 1.5 Bi 0.5− x Te 3 samples ( x = 0–0.5) were successfully synthesized via a fast and cost-effective process, mechanical alloying followed by cold pressing and sintering. Structural characterization using powder x-ray diffraction (PXRD) and scanning electron microscopy (SEM) confirmed highly textured, layered structures consistent with Bi 2 Te 3 and Sb 2 Te 3 , except in samples with x = 0.5. Transport measurements showed that increasing dopant concentration decreased the Seebeck coefficient while increasing electrical conductivity, attributed to electron donation from B, Ba, and Yb atoms. Thermal conductivity also increased with dopant content, likely owing to enhanced electronic contributions. The maximum thermoelectric figure of merit ( ZT ) of 1.1 was achieved for Bi 1.9 Yb 0.1 Te 3 and Sb 1.5 Bi 0.4 B 0.1 Te 3 at 373 K. Boron proved more effective for p -type BiSbTe, whereas ytterbium was superior for n -type compounds. ZT improved by at least 15% for p -type and 30% for n -type BiSbTe compared with pristine samples. These results indicate that substituting Bi atoms with metals of high electronegativity and larger atomic radii effectively tunes transport properties and enhances the thermoelectric performance of BiSbTe compounds.