Bismuth antimony telluride compounds are among the well-known thermoelectric materials. In this research, Bi0.5Sb1.5Te3 powder was synthesized by the ball milling process for 12 h. Afterward, thermal evaporation in a vacuum of about 10-6 torr was followed to deposit Bi0.5Sb1.5Te3 thin films with various thicknesses (138, 190, and 290 nm). X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to identify the microstructure, composition, and morphology of the synthesized powder and the deposited thin films. The phase analysis and microstructural characterization results of the synthesized powder showed that the Bi0.5Sb1.5Te3 compound is formed and its microstructure includes nano-sized grains. Thermoelectric properties of the thin films were examined by room temperature measurement of the average Hall coefficient, carrier concentration, Seebeck coefficient, and electrical conductivity. Thermoelectric results demonstrated that the thin film with a lower thickness (138 nm) shows a sheet concentration of 1.0403*1015cm-2 at 323 K in comparison with the thicker samples (190 nm and 290 nm). Furthermore, the Seebeck coefficient decreased from 204 to 133.48 µV/K at 323 K when the sample thickness was increased from 138 to 290 nm. Compared with the thin film with the highest thickness (290 nm) which its power factor was measured as 1.29 µW/K2.cm at 323 K, the power factor of the thin film with the lowest thickness (138 nm) was as high as 1.861 µW/K2.cm.

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