In order to elucidate the stability of a silicon oxide layer on ZnO, the dynamic behavior of SiO- and SiO2-layer-coated ZnO ultrafine particle surfaces were directly observed by heating in a transmission electron microscope up to 700°C. In the case of SiO-coated ZnO ultrafine particles, ZnO nanocrystallites with the size of 2nm grew in the SiO layer at 500°C. In the case of SiO2-coated ZnO ultrafine particles, β-cristobalite with the size of 10nm order was grown at 600°C. Zn2SiO4 particles were grown by coalescence between β-cristobalite and ZnO at 700°C. By comparing the SiO and SiO2 layers on ZnO ultrafine particles, it was found that the behaviors of the two silicon oxide layers are clearly different.
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