Composition and Structure of Ti-based Hydroxyfluoride

As already mentioned in Chapter 2 of this book, the [HF] content is a relevant parameter since it allows the stabilization of several phases in an aqueous medium. Focusing on the R = [HF]/[Ti] = 3 molar ratio, the synthesis operated at T = 90 °C with Ti oxychloride as precursor enables the preparation of a single phase related to TiOF2 type structure as revealed by X-ray diffraction analysis with crystallite size around 80 nm. Interestingly, an 

The effect of the nature of the synthesis medium has also been considered through the replacement of both titanium precursor and solvent. An organic medium has therefore been used containing titanium isopropoxide as precursor and isopropanol as solvent. In these conditions, two different R = [HF]/[Ti] molar ratios have been studied, i.e. 3 and 4. The corresponding X-ray diffraction powder patterns (not shown) are similar to those obtained from the aqueous medium with a broadening of the X-ray peaks suggesting smaller particle size. Here, the salient point is that the recovered powders are coloured, which is consistent with mixed-valency Ti. Such a point will be discussed later. 

Structural properties of titanium hydroxyfluorides were characterized by X-ray and neutron powder diffraction. For X-ray characterization, diffraction data were recorded on a 

25O1s7Fo.17 composition recorded on two single grains. Reproduced with the permission of ACS or American Chemical Society 

The diffraction data were analysed using the Rietveld technique as implemented in the Fullprof Suite Program. Peak shape was described by a pseudo-Voigt function, and the background level was fitted with linear interpolation between a set of given points. 

---