Anatase and brookite TiO2 with various morphologies and their proposed building block

Abstract

In this work, brookite TiO₂ has been synthesized by a simple hydrothermal approach using sodium titanate as a precursor in the presence of a sodium fluoride aqueous solution. The ratio of brookite and anatase TiO₂ can be tailored by the NaF concentration. In a concentrated NaF solution, high quality brookite TiO₂ was acquired. Pure anatase nanoparticles were obtained in only deionized water. Moreover, the morphology and size of brookite TiO₂ can be tailored by using various acid treated titanates which influence the stability of the building blocks and nucleation points of TiO₂. Micro-sized flower-like brookite, submicro-sized urchin-like brookite and brookite nanorods with anatase nanoparticles were obtained. The micro-sized flower-like brookite remains the same shape and phase even at 800 °C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 °C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 °C and 100% grain-like rutile was obtained at 900 °C.