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 TiOF2 possesses a simple cubic structure (space group Pm (3) over barm) at room temperature. Three-dimensional nanostructured assemblies of polycrystalline TiOF2 have recently been synthesized via chemical conversion of intricate SiO2 structures by metathetic reaction with TiF4(g). Rietveld analysis has been used to evaluate the structure of the TiOF2 product formed by such reaction at 623 K. Unlike prior reports, this TiOF2 product possessed a hexagonal structure (space group R (3) over barc) at room temperature. Upon heating through 333-338 K, the hexagonal TiOF2 polymorph converted into cubic (Pm (3) over barm) TiOF2. Differential scanning calorimetry and X-ray diffraction analyses have been used to evaluate this thermally induced phase transformation.