Hexagonal and cubic TiOF2

The chemical, electrochemical, optical and electro-optical properties of titanium oxyfluoride, TiOF2, have led to interest in this compound for a number of applications. Prior analyses have indicated that TiOF2possesses a simple cubic structure (space groupPm{\overline 3}m) at room temperature. Three-dimensional nanostructured assemblies of polycrystalline TiOF2have recently been synthesizedviachemical conversion of intricate SiO2structures by metathetic reaction with TiF4(g). Rietveld analysis has been used to evaluate the structure of the TiOF2product formed by such reaction at 623 K. Unlike prior reports, this TiOF2product possessed a hexagonal structure (space groupR{\overline 3}c) at room temperature. Upon heating through 333–338 K, the hexagonal TiOF2polymorph converted into cubic (Pm{\overline 3}m) TiOF2. Differential scanning calorimetry and X-ray diffraction analyses have been used to evaluate this thermally induced phase transformation.