Hexagonal and cubic TiOF₂

Abstract

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 group Pm3m) at room temperature. Three-dimensional nanostructured assemblies of polycrystalline TiOF₂have recently been synthesized via chemical conversion of intricate SiO₂structures by metathetic reaction with TiF₄. 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 R3c) at room temperature. Upon heating through 333–338 K, the hexagonal TiOF₂ polymorph converted into cubic (Pm3m) TiOF₂. Differential scanning calorimetry and X-ray diffraction analyses have been used to evaluate this thermally induced phase transformation.