Grain growth in nanocrystalline SnO₂ prepared by sol-gel route

The isothermal grain growth of nanocrystalline SnO₂, prepared by the sol-gel route was investigated at various temperatures between 500 °C and 800 °C. Grain growth data were analyzed using two different models. A conventional grain growth model for polycrystalline materials yields an extremely low activation energy of 47 kJ/mol, but large grain growth exponent n from 5 to 11. These values exceed the rational region deduced from conventional theory. An alternative model is based on the assumption that the ordering of the interface regions in nanocrystalline SnO₂ occurs simultaneously with grain growth by structural relaxation. This structural relaxation model describes the grain growth kinetics satisfactorily and also yields a low activation energy of 31 kJ/mol appropriate for the rearrangement of atoms.