Sulfurization temperature induced enhancement in thermoelectric properties of polycrystalline WS2 nanomaterials

We have presented an interesting study about the evolution of vibrational modes in WS2 nanostructures and their effect on material thermoelectric performance. High purity polycrystalline nanostructures of WS2 were prepared by sulfurizing the hydrothermally prepared WS2 powders at different temperatures. The effect of sulfurization temperature on the structure of WS2 nanomaterials was probed by XRD and Raman Spectroscopy. XRD data confirmed the crystal structure of WS2 along with the presence of WO3 based secondary phases. An experimental investigation of the phase changes with sulfurization temperature has been made by Raman scattering methods. Both in Plane (E12g) and out of plane (A1g) Raman modes exhibited red shift by 45 and 11 cm−1 respectively and variation in Raman peak intensity with sulfurization temperature was also observed. For all samples, the room temperature thermoelectric measurements reveal that an increase in sulfurization temperature from 300 to 823 k resulted in the enhancement of electrical conductivity and the Seebeck coefficient. The observed thermoelectric data was linked with the structural changes occurred during the increase of sulfurization temperature. Power factor of WS2 nanostructures increase up to 5.09x 10−3 Wm−1K−2 with increasing sulfurizing temperature.