The soft chemical synthesis of TiO2 (B) from layered titanates

Abstract

Proton exchange and subsequent dehydration of layered titanates with the formula A2TinO2n+1 (A = Na, K, Cs; 3 ≤ n ≤ 6) yield TiO2 (B) at temperatures below 350°C. In order to elucidate the mechanism of TiO2 (B) formation, we have characterized these reactions using thermal analysis and crystallographic techniques, and we have examined the effect of different starting materials on the formation of TiO2 (B). The dehydration proceeds through three distinct steps: an initial topotactic structural condensation, which is endothermic, followed by an exothermic nucleation and growth step that results in the formation of a TiO2 (B)-like intermediate, and a final, low-energy transformation, which yields TiO2 (B). The structures of D2Ti3O7 and TiO2 (B) have been refined from powder neutron diffraction data in order to better understand the relationship between the initial titanate structures and the formation of TiO2 (B).