Microcrystalline phase transformation from ZrF_4?HF?2H_2O to ZrO_2 through the intermediate phases ZrF_4?3H_2O, ZrF_4?H_2O, Zr_2OF_6?H_2O and ZrF_4

摘要

The behavior of hydrated zirconium fluoride has been studied by perturbed angular correlation spectroscopy. It is found that the crystalline compound ZrF_4?HF?2H_2O, formed initially by drying solution of Zr metal in concentrated HF, transforms spontaneously to ZrF_4?3H_2O. This trihydrated compound dehydrates to ZrF4 through the intermediate monohydrates ZrF_4?H_2O and Zr_2OF_6?H_2O. The compound ZrF4 finally transforms to ZrO_2 at ~343 K. Different crystalline phases of ZrF_4?HF?2H_2O, ZrF_4?3H_2O, ZrF_4?H_2O, Zr_2OF_6?H_2O, ZrF_4 and ZrO_2 have been identified and characterized by PAC spectroscopy. From previous PAC measurements, the intermediate ZrF_4?H_2O and Zr_2OF_6?H_2O were not observed and the dehydration from ZrF_4 ?3H_2O to ZrF_4 was found to be routed directly. Present measurements by PAC exhibits dissimilar crystal structures for ZrF_4?3H_2O and ZrF_4?H_2O unlike the crystal structures found in hafnium analogous compounds.