Preparation of high-purity ZrF_4 and HfF_4 for optical fibers and radiation-resistant glasses

摘要

The separation coefficients of ZrF_4(HfF_4)and metal fluoride impurities in the process of vacuum sublimation between 900 and 1200 K in the molecular vaporization regime were calculated. The separation coefficients were found to decrease in the order CrF_2 > MnF_2 >NiF_2 >CoF_2 > MnF_3 > FeF_2 >AlF_3 > CrF_3 > CuF_2 > FeF_3. The conditions for purification of ZrF_4 and HfF_4 by vacuum sublimation were optimized. The Total impurity content in both fluorides was found to increase with the product of the evaporation rate per unit Area and the degree of evaporation.