Influense of KI addition on the interactions in KF–KCl containing K2SiF6 and SiO2

A. V. Isakov, A. O. Khudorozhkova, E. G. Vovkotrub, A. S. Vorob’ev, A. A. Red’kin, Yu. P. Zaikov. 

ABSTRACT

       The interaction of KI with the KF–KCl–K₂SiF₆ and KF–KCl–K2SiF₆–SiO₂ salt systems was studied. The KF–KCl and KF–KCl–KI systems containing both K₂SiF­₆ and SiO₂ were studied by Raman spectroscopy. It was shown that the addition of KI to the KF–KCl–K₂SiF₆ and KF–KCl–K₂SiF₆–SiO₂ melts leads to the appearance of groups containing Si–I bonds in the solid samples. It was established that a significant part of silicon dioxide from the KF–KCl–K₂SiF₆–SiO2 and KF–KCl–KI–K₂SiF₆–SiO₂ melts crystallizes in the form of silicate structures characteristic of the K₂SiO₃ phase (K₂O · SiO₂). The Raman spectroscopy data are consistent with the data of X–ray phase analysis of KF–KCl and KF–KCl–KI melts containing both K₂SiF₆ and SiO₂. It was found that the crystallization field of K₃SiF₇ is retained when KI is added to the KF–KCl–K₂SiF₆ and KF–KCl–K₂SiF₆–SiO₂ melts. When KI is introduced into the melt, it is characteristic to precipitate it into a separate phase during crystallization. Low–intensity peaks corresponding to the crystallization of the α-SiO₂ phase were recorded for the KF–KCl–K₂SiF₆–SiO₂ and KF–KCl–KI–K₂SiF₆–SiO₂ systems.

    The study of KF–KCl–KI–K₂SiF₆ and KF–KCl–KI–K₂SiF₆–SiO₂ melts by the method of synchronous thermal analysis was carried out. It was found that at temperatures up to 473 K, phase transitions are observed, which are probably associated with the transformation of SiI_xF_y^z– structures into structures containing SiF₆^2–, which is consistent with information on the thermal stability of mixed silicon halide.

KEY WORDS:

potassium fluoride, potassium chloride, potassium iodide, siliceous melts, Raman spectroscopy, X–ray phase analysis, STA analysis.

DOI: 10.31857/S0235010621010047