Microstructural and Thermoelectric Properties of Heat-treated Al<sub>2</sub>O<sub>3</sub> Doped BiSbTe Alloy

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).