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 image. 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.