Enhanced thermoelectric performance of heat-treated hybrid composites of gas atomized p -type Bi 0.5 Sb 1.5 Te 3 /Ta 2 O 5 alloy

Bismuth-telluride (Bi₂Te₃) based alloys are highly efficient thermoelectric (TE) materials for energy conversion near room temperature. This study fabricated a hybrid composite of p-type Bi_0.5Sb_1.5Te₃ (BST)/Ta₂O₅ alloys via high-energy ball milling. The BST alloys exhibit a rhombohedral structure and a reduction in particle size upon Ta₂O₅ doping. In addition, the distinct distribution of Ta₂O₅ nanoparticles in the matrix was noticed. An enhancement in the Seebeck coefficient, reaches a maximum of 256 µV/K at 300 K for hybrid composites despite their drop in the electrical conductivity, realizing the energy carrier filtering. On the other hand, a marginally reduced thermal conductivity of 0.89 W/m. K. was observed compared to pristine BST due to multiple alloy disorder. Furthermore, the heat-treated composite exhibited improved electrical conductivity of 496 S/cm at 300 K, substantially reaching a figure of merit, zT of 0.96. However, pristine BST showed a maximum zT of 1.23 at 350 K due to its superior power factor of 3.25 × 10⁻³ W/m·K². These findings demonstrate that microstructural modifications and heat treatment can effectively tune thermoelectric properties, offering insights for further material optimization.