The demand for a dense zirconium tetrafluoride of high purity for use in the preparation of zirconium metal can be met by vacuum sublimation of zirconium fluoride prepared by the precipitation and dehydration method. Separation of zirconium fluoride from less volatile metallic impurities, moisture, and non-volatile zirconium compounds was accomplished in this manner. The degree of separation of the desired product improved with the use of lower sublimation temperatures; the lowest temperature was 750 degrees centigrade. Some fractionation from hafnium also occurred at this temperature, but zirconium tetrafluoride was the more volatile so a complete separation of zirconium from hafnium by sublimation does not seem practical.
Abate, Louis J. and Wilhelm, Harley A., "Sublimation of zirconium tetrafluoride" (1951). Ames Laboratory ISC Technical Reports. 21.