Microstructural and Thermoelectric Properties of Heat-treated Al₂O₃ Doped BiSbTe Alloy

Abstract

In this study, the microstructural and thermoelectric transport properties of Al₂O₃ nanofibers (6 wt. %) doped heat-treated p-type BiSbTe (BST)/Al₂O₃(F) composites were studied. The findings were compared with those of BST/Al₂O₃(S) composites containing spherical Al₂O₃ particles. Initially, BiSbTe powder was manufactured using a water-atomization technique, and BST/Al₂O₃ composite powders were prepared through mechanical alloying, followed by spark plasma sintering to achieve a bulk compact specimen. Further, the bulk composites were heat treated at 743 K to evaluate the thermoelectric properties of the Al₂O₃ doped BiSbTe alloy. The powder morphology of BST/Al₂O₃ milled powder is irregular and in the range of tens of micrometers. The bulk composites' fracture surface showed the lamellar microstructure with random orientations. The temperature-dependent electrical conductivity (σ) trend indicates the highly degenerate semiconducting behavior with marginal variations for both the composites and the +Ve sign of the Seebeck coefficient (S) with its maximum of 206 μV/K at 425K for the BST/Al₂O₃(S) composite. Finally, the maximum power factor (S²σ) of 2.0 mW/m. K² at 325K was observed for BST/Al₂O₃(S).