High-energy ball milling—a possible synthesis route for cryolite and chiolite

Mixtures of powders of crystalline sodium fluoride together with crystalline or amorphous aluminium fluoride were mechanically treated at ambient temperature by high-energy ball milling using a planetary mill. The application of X-ray powder diffraction together with 19F and 27Al MAS NMR spectroscopy gave unambiguous evidence that solid state chemical reactions between NaF and AlF3 take place at mechanical milling. Dependent on the molar ratio of the educts cryolite (Na3AlF6) and/or chiolite (Na5Al3F14) are obtained as reaction products. Moreover, the state of order of the educts, here crystalline or amorphous aluminium fluoride, has a strong influence on the reaction products formed.

Figure optionsDownload as PowerPoint slide