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Amorphous powders of undoped and chromium-doped TiO2 were prepared by a sol-gel method. Corresponding crystalline (anatase/rutile) phases were obtained by thermally-induced transformation of these amorphous powders. The activation energies for crystallization and grain growth of crystalline TiO2 and Ti0.9Cr0.1O2 from respective amorphous counterparts were estimated from X-ray diffraction and differential thermal analysis studies. The activation energies required for grain growth in amorphous TiO2 and Ti0.9Cr0.1O2 samples, were 1.51 kJ/mol and 1.78 kJ/mol, respectively. The activation energies required for the phase transformation from amorphous to crystalline TiO2 and Ti0.9Cr0.1O2 were 132 kJ/mol and 153 kJ/mol, respectively. It has been clearly demonstrated that relatively a higher temperature is required for the phase transformation in amorphous Cr doped TiO2 than in amorphous TiO2. This can be attributed to the high energy required for the substitution of Cr at Ti site in the TiO2 lattice, which in turn also yields a smaller crystallite size during grain growth.
