Microstructural control of the TiO₂-SnO₂ binary system and synthesis of SnO₂ nanowhiskers by microwave irradiation

SnO₂ single crystals (columnar crystals and silver grass-like nanowhiskers) were synthesized by selective microwave heating of a TiO ₂-SnO₂ mixture. The shape of the as-grown SnO₂ crystals is strongly dependent on the atmosphere during microwave irradiation. This is due to the difference in growth mechanisms, as revealed by in-situ surface observation under microwave irradiation, in addition to scanning and transmission electron microscopy observations of irradiated specimens. In a N₂ atmosphere, silver grass-like SnO₂ nanowhiskers were obtained. On the other hand, columnar SnO₂ crystals were obtained in air or an O₂ atmosphere. Photoluminescence and absorption spectra of the as-grown SnO₂ crystals were examined. Based on the analysis of a TiO₂-SnO₂ pellet, it was found that the bottom was selectively heated, and SnO₂ sublimated by microwave irradiation. A density gradient texture of the sample pellet was formed.