STRUCTURAL TRANSITION OF NANOCRYSTALLINE TiO2.

Nanocrystalline TiO2 sample was prepared by high-energy ball mill method. A known quantity of anatase phase-TiO2 was milled for 83 h in air. The samples were collected at intervals of 5 h of milling. The XRD patterns were recorded for all the samples. The crystal structure changed from anatase phase for bulk material to rutile-rich phase for nanocrystalline material. Nanocrystalline TiO2, which is a mixture of anatase, rutile, and srilankite phase, was prepared by milling for 60 h. The XRD pattern of unmilled anatase phase of TiO2 could be refined with I41/amd space group. The crystallite size of the TiO2 was found to decrease with milling time upto 50 h and then the size of rutile phase increases while the sizes of anatase and srilankite phases remain constant upto 60 h of milling. After 60 h, the sizes of all the phases remain constant. The average crystallite size for rutile phase is found to be 12 nm after 60 h of milling. [ABSTRACT FROM AUTHOR]