Enhancement of thermoelectric power factor of hydrothermally synthesised SrTiO<sub>3</sub> nanostructures
N. Yalini Devi, P. Rajasekaran, K. Vijayakumar, A.S. Alagar Nedunchezhian, D. Sidharth, G. Anbalagan, M. Arivanandhan, R. Jayavel
Abstract
Abstract Strontium Titanate (SrTiO 3 ) nanoparticles were synthesised by varying the hydrothermal growth period as 12, 24 and 48 h. The crystal structure, morphology, functional groups and elemental composition of the prepared SrTiO 3 nanoparticles were studied using XRD, FESEM, Raman and XPS, respectively. XRD analysis shows that the intensity of the diffraction peaks of SrTiO 3 increased with growth period due to high crystallinity of the hydrothermally grown samples. From the FESEM images, it was observed that the morphology of SrTiO 3 was changed from spherical to cubic when the hydrothermal growth period increased from 12 to 24 h. The different modes of vibration of samples were studied using Raman spectroscopy. XPS substantiate the composition and binding states of each element in the sample. The Seebeck coefficient and electrical resistivity of the prepared SrTiO 3 nanostructures were measured at various temperatures by pelletizing the samples. The Seebeck coefficient of the sample gradually increased with hydrothermal growth period. The electrical resistivity of the sample relatively decreased with growth period. The power factor of the samples was calculated from the obtained Seebeck coefficient and electrical resistivity. A power factor of the sample prepared at 24 h of hydrothermal growth (2.191 × 10 −4 W.m −1 .K −2 at 550 K) was two order higher than that of as prepared sample (0.012 × 10 −4 W.m −1 .K −2 at 550 K). The experimental results revealed that the increase in hydrothermal growth period has a potential effect on the morphology. The cubic morphology with high crystalline nature facilitated the electron transport thereby thermoelectric power factor was enhanced in SrTiO 3 nanostructures.