Grain growth in nanocrystalline SnO2 prepared by sol-gel route

The isothermal grain growth of nanocrystalline SnO2, prepared by the sol-nel route was investigated at various temperatures between 500 degrees C and 800 degrees 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. (C) 1999 Acta Metallurgica Inc.