Thermal study of hafnium fluoride compounds to prepare hafnium oxofluorides

Using the methods of periodic weighing, X-ray diffractometry and chemical analysis at the temperatures 260-410 deg C, partial pressures of water vapours 1.85-2.5 kPa, thermal behaviour of powder-like hafnium tetrafluoride monohydrate and ammonium hexafluorohafnate with specific surface 2.3; 2.0 m2/g, particle size < 0.016 mm, have been investigated. It is shown, that in the process of heating (NH4)2Hf6 at 400 deg C forms oxofluoride of the composition HfOF2. For the given compound the space group (P2111) is established and unit cell parameters are calculated: a=6.38, b=8.20, c=13.12 A. Calculation of kinetic parameters of HfOF2 formation reaction (n < 1, Esub(apparent) = 98+-13 kJ/mol) is made