Thermal decomposition of HfCl4 as a function of its hydration state

The thermogravimetric behavior of HfCl4 powders with different hydration states has been compared. Strongly hydrated powders consist of HfOCl2·nH2O with n>4n>4. Partially hydrated powders consist of particles with a HfCl4 core and a hydrated outerlayer of HfOCl2·nH2O with n in the range of 0–8. Hydrated powders decomposed at temperature lower than 200 °C whereas the decomposition of partially hydrated powders was completed at a temperature of around 450 °C. The observed differences in decomposition temperature is related to the structure of HfOCl2·nH2O, which is different if n is higher or smaller than 4 and leads to intermediate compounds, which decompose at different temperatures.

Octahedral chains in ZrCl4 [B. Krebs, Angew. Chem. Int. Ed. 8 (1969) 146–147].Figure optionsDownload as PowerPoint slide