Effect of Ga on the Morphology of SnO₂ Nano/Micro-Crystals Grown by a Thermal Evaporation Method

Abstract

SnO<sub>2</sub> nano/micro-crystals with different morphologies were fabricated by the thermal evaporation of SnO<sub>2</sub> powders mixed with Ga<sub>2</sub>O<sub>3</sub> powder. The synthesis process was performed at 1300℃ in air. X-ray diffraction (XRD) analysis, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to examine the morphology, microstructure, elemental composition and chemical property of the as-synthesized products. X-ray diffraction analysis revealed that the products were SnO<sub>2</sub> with a tetragonal rutile crystal structure. From the Fourier transform infrared spectra of the products, Sn-O stretching mode was observed, which confirmed the formation of SnO<sub>2</sub>. Scanning electron microscopic analysis clearly showed that the morphology of the SnO<sub>2</sub> crystals was significantly affected by the addition of Ga<sub>2</sub>O<sub>3</sub> to SnO<sub>2</sub> source powder. SnO<sub>2</sub> crystals with a belt-like morphology were grown when the source powder without Ga<sub>2</sub>O<sub>3</sub> powder was used. Rod-like SnO<sub>2</sub> crystals were grown by using SnO<sub>2</sub> powder mixed with Ga<sub>2</sub>O<sub>3</sub> powder as the source powder. When the amount of Ga<sub>2</sub>O<sub>3</sub> mixed in the source powder was increased, the morphology of the SnO<sub>2</sub> crystals changed from rod to tube. Energy dispersive X-ray analysis indicated that the inner core of the tube-like crystals was composed of Snrich metastable phase. No catalytic particles were observed at the tips of the SnO<sub>2</sub> nano/micro-crystals, suggesting that the growth process occurred by vapor-solid growth mechanism.