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

SnO₂ nano/micro-crystals with different morphologies were fabricated by the thermal evaporation of SnO₂ powders mixed with Ga₂O₃ 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 SnO₂ 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 SnO₂. Scanning electron microscopic analysis clearly showed that the morphology of the SnO₂ crystals was significantly affected by the addition of Ga₂O₃ to SnO₂ source powder. SnO₂ crystals with a belt-like morphology were grown when the source powder without Ga₂O₃ powder was used. Rod-like SnO₂ crystals were grown by using SnO₂ powder mixed with Ga₂O₃ powder as the source powder. When the amount of Ga₂O₃ mixed in the source powder was increased, the morphology of the SnO₂ 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 SnO₂ nano/micro-crystals, suggesting that the growth process occurred by vapor-solid growth mechanism.