Article: Effect of brookite presence on nanocrystalline anatase – rutile phase transformation Journal: International Journal of Nanotechnology (IJNT) 2009 Vol.6 No.10/11 pp.961 - 972 Abstract: TiO<SUB align="right">2</SUB> nanocrystals were prepared by hydrolysis and peptisation of titanium isopropoxide under different pH values. The as-prepared powder of very fine anatase crystallites ranges from 8 nm in acidic solution of pH 3 to 10 nm in basic solution of pH 8. Heat treatment of the powders leads to grain growth and anatase-rutile transformation. Experimental results have shown that the anatase to rutile phase transformation in the heat-treated powders depend not only on primary crystallite size but also the presence of brookite phase. It is observed that in the powders with the same size the presence brookite phase would accelerate the anatase to rutile transformation. Furthermore it has been found that the transition route is different among samples prepared in acidic or basic solutions. It is also proved that in case of acidic solutions, the transition route follows the brookite-anatase-rutile path, but in case of basic solutions, it would be done via anatase-brookite-rutile. Apart from these observed paths, the main route of A-R remains unchanged for both acidic and basic conditions. So it could be justified that brookite phase together with anatase grain size in titania powder plays very important and different roles and accelerates phase transformation. Inderscience Publishers - linking academia, business and industry through research

Title: Effect of brookite presence on nanocrystalline anatase – rutile phase transformation

Authors: Sara Mahshid, Masoud Askari, Morteza Sasani Ghamsari

Addresses: Material Science and Engineering Department, Sharif University of Technology, 11155-9466, Tehran, Iran. ' Material Science and Engineering Department, Sharif University of Technology, 11155-9466, Tehran, Iran. ' Solid State Lasers Research Group, Laser & Optics Research School, NSTRI, Tehran, 11365-8486, Iran

Abstract: TiO₂ nanocrystals were prepared by hydrolysis and peptisation of titanium isopropoxide under different pH values. The as-prepared powder of very fine anatase crystallites ranges from 8 nm in acidic solution of pH 3 to 10 nm in basic solution of pH 8. Heat treatment of the powders leads to grain growth and anatase-rutile transformation. Experimental results have shown that the anatase to rutile phase transformation in the heat-treated powders depend not only on primary crystallite size but also the presence of brookite phase. It is observed that in the powders with the same size the presence brookite phase would accelerate the anatase to rutile transformation. Furthermore it has been found that the transition route is different among samples prepared in acidic or basic solutions. It is also proved that in case of acidic solutions, the transition route follows the brookite-anatase-rutile path, but in case of basic solutions, it would be done via anatase-brookite-rutile. Apart from these observed paths, the main route of A-R remains unchanged for both acidic and basic conditions. So it could be justified that brookite phase together with anatase grain size in titania powder plays very important and different roles and accelerates phase transformation.

Keywords: hydrolysis; peptisation; anatase; rutile; brookite; phase transformation; TiO2 nanocrystals; titanium dioxide; Iran; nanotechnology.

DOI: 10.1504/IJNT.2009.027559

International Journal of Nanotechnology, 2009 Vol.6 No.10/11, pp.961 - 972

Published online: 31 Jul 2009 *

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Title: Effect of brookite presence on nanocrystalline anatase – rutile phase transformation

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