Grain growth kinetics of SnO₂ nanocrystals synthesized by precipitation method

Abstract

Monodispersed spheroidal SnO₂ nanocrystals with the grain size of 8–30 nm were synthesized by the precipitation method using SnCl₄·5H₂O (stannic chloride hydrate) as raw materials. Differential scanning calorimetry/thermogravimetry (DSC/TG), X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize the structure of SnO₂ nanocrystals. The influences of the calcination temperature and time on the lattice constant, the lattice distortion and the grain size of SnO₂ nanocrystals were discussed based on the XRD results. The grain growth kinetics of SnO₂ nanocrystals during calcination process was simulated with a conventional grain growth model which only took into account of diffusion and with a new isothermal model proposed by our group, which took into account of both diffusion and surface reactions. Using conventional model, the grain growth rate constant of SnO₂ crystals is 1.55×10⁴ nm⁵/min with a pre-exponential factor of 5 and an activation energy of 108.62 kJ/mol. Compared with the convention model, the new isothermal model is more realistic in reflecting the grain growth behavior of SnO₂ nanocrystals during the calcination process. This indicates that the grain growth of SnO₂ nanocrystals is controlled by both diffusion and reaction factors, and the effect of surface reactivity on the grain growth of SnO₂ nanocrystals could not be ignored. A combined activation energy estimated with the new isothermal model is 53.46 kJ/mol.

Keywords

SnO₂ nanocrystal / precipitation method / calcination / grain growth kinetics

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