Crystal growth of tin oxide nano-sheets in aqueous solutions and time variation of N2 adsorption characteristics

Abstract

Nucleation and crystal growth of tin oxide were realized in aqueous solutions. Nano-sheet structures grew in the solutions containing SnF2 at 90 °C to develop in-plane size and thickness gradually. Their color, size, morphology, crystal structure and N2 adsorption property varied with progress of crystal growth. Color of powder changed from white to light yellow, light blown to light green particles with growth. XRD analyses clarified that single phase of SnO2 was synthesized in the aqueous solutions without high temperature annealing. It is an advantage to conventional ceramic firing process. Growth curves of crystallite size were consistent with morphological observations using Field Emission Scanning Electron Microscopy FE-SEM. Development of sheet structure was caused by crystal growth of SnO2. Large crystallite size perpendicular to (200) planes indicated that growth along c-axis was suppressed compared to a-axis. Anisotropic crystal growth resulted anisotropic shape of nano-sheets. Chemical composition of fluorine-doped SnO2 nano-sheets was estimated to Sn : F = 1 : 0.06–0.12. BET surface area increased with crystal growth and reached to 85 m2/g. It gradually decreased with synthesis period. Growth of sheet structure along in-plane direction related to increase of surface area. Further growth in thickness increased volume of the sheets to cause decrease of surface area per weight. N2 adsorption property strongly related to crystal growth and shape change of the nano-structures. The system has the advantage of morphology controllability of tin oxide nano-structure and low environmental load.