Crystal structure and thermal properties of a new double salt: K2SiF6.KNO3 by C. Rissom, H. Schmidt, and W. Voigt

Crystal Research and Technology

Cryst. Res. Technol. 43, 74 (2008) - Abstract -

Crystal structure and thermal properties of a new double salt: K₂SiF₆^.KNO₃

C. Rissom, H. Schmidt, and W. Voigt

TU Bergakademie Freiberg, Institut für Anorganische Chemie, Leipziger Str. 29, 09596 Freiberg, Germany

Keywords	hexafluorosilicate, double salt, crystal structure, solubility, thermal properties, Raman spectroscopy
PACS	61.10.Nz, 61.66.Fn, 64.70.Dv, 64.70.Kb, 64.75.+g, 81.30.Mh, 81.70.Pg, 87.64.Je
DOI	10.1002/crat.200711050

A new double salt K₂SiF₆^.KNO₃ was found during determination of the solubility of K₂SiF₆ in aqueous potassium nitrate solutions. Unit cell parameters (P6₃/mmc, a = 5.6268(1) Å, c = 14.5186(6) Å, V = 398.09(2) Å³, Z = 2) and crystal structure have been determined. The compound is further characterized by RAMAN spectroscopy and X-ray powder diffraction. Thermal properties were studied using DTA, DSC and in situ high- temperature X-ray powder diffraction measurements. At 287°C K₂SiF₆^.KNO₃ decomposes into its components KNO₃ and K₂SiF₆ with an enthalpy of decomposition of about + 42 J∙g^-1. Further thermal effects could be assigned to phase transformations of KNO₃ whereby earlier literature data have been reconfirmed.

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