Effect of Hydrothermal Synthesis Temperature on the Microstructural and Thermoelectric Characteristics of Thermally Deposited Bi0.5Sb1.5Te3 Thin Films

Bismuth antimony telluride (Bi_0.5Sb_1.5Te₃) is a ternary compound with good thermoelectric properties at near room temperature. In this research, Bi_0.5Sb_1.5Te₃ powders were hydrothermally synthesized at different temperatures (100, 150, 190, and 230°C) for 24 h. The deposition procedure of Bi_0.5Sb_1.5Te₃ thin films was done by using thermal evaporation. The phases and microstructures of powders and thin films were investigated by x-ray diffraction and field emission scanning electron microscopy. Moreover, the size distribution of powders was investigated using a particle size analyzer. The phase and microstructural results of the different synthesized powders confirmed that the Bi_0.5Sb_1.5Te₃ thin film prepared by powder synthesis at 150°C for 24 h is the best choice for manufacturing with good thermoelectric properties because of its nano-sized grains and high purity. The results showed that the Bi_0.5Sb_1.5Te₃ thin film fabricated by powders synthesized at 150°C has a single rhombohedral phase with a good semiconductor performance. The results of thermoelectric tests confirmed that the Bi_0.5Sb_1.5Te₃ thin film fabricated using a hydrothermal method and thermal evaporation deposition approach shows a high Seebeck coefficient (183.5 μV/K) and low electronic thermal conductivity (1.32 × 10⁻⁴ W/m k⁻¹) at 298 K. Besides, the power factor values of 0.7, 2.59 and 2.9 μW/cm K⁻² were obtained at 298, 373 K and 473 K, respectively.