Solid state reactions of hexafluorosilicates

At beginning thermal decomposition K₂SiF₆] loses SiF₄-planes from SiF₆]^2?-octahedrons, which has been proved by x-ray-diffraction 1], 2]. Analogous disorder structures are supposed to be present with all solids having complex ions including carbonates, sulfates and others. The result is a high reactivity at this spots. Another reactive form in hexefluorosilicates is represented by mobile SiF-species, perhaps SiF₃⁺. The reactivity is shown by heterogenous reactions with CHCl₃ and by solid-solid reactions for instance with halides, oxides etc. As an example corundum (α-Al₂O₃) reacts at 600°C giving K₃ AlF₆ and KAlSiO₄ 3].