Microcrystalline phase transformation from ZrF4·HF·2H2O to ZrO2 through the intermediate phases ZrF4·3H2O, ZrF4·H2O, Zr2OF6·H2O and ZrF4

The behavior of hydrated zirconium fluoride has been studied by perturbed angular correlation spectroscopy. It is found that the crystalline compound ZrF4·HF·2H2O, formed initially by drying solution of Zr metal in concentrated HF, transforms spontaneously to ZrF4·3H2O. This trihydrated compound dehydrates to ZrF4 through the intermediate monohydrates ZrF4·H2O and Zr2OF6·H2O. The compound ZrF4 finally transforms to ZrO2 at ∼343 K. Different crystalline phases of ZrF4·HF·2H2O, ZrF4·3H2O, ZrF4·H2O, Zr2OF6·H2O, ZrF4 and ZrO2 have been identified and characterized by PAC spectroscopy. From previous PAC measurements, the intermediate ZrF4·H2O and Zr2OF6·H2O were not observed and the dehydration from ZrF4·3H2O to ZrF4 was found to be routed directly. Present measurements by PAC exhibits dissimilar crystal structures for ZrF4·3H2O and ZrF4·H2O unlike the crystal structures found in hafnium analogous compounds.