Zirconium tetrafluoride
Zirconium(IV) fluoride describes members of a family inorganic compounds with the formula ZrF4(H2O)x. All are colorless, diamagnetic solids. Anhydrous Zirconium(IV) fluoride is a component of ZBLAN fluoride glass.[1]
Structure
Three crystalline phases of ZrF4 have been reported, α (monoclinic), β (tetragonal, Pearson symbol tP40, space group P42/m, No 84) and γ (unknown structure). β and γ phases are unstable and irreversibly transform into the α phase at 400 °C.[2]
Zirconium(IV) fluoride forms several hydrates. The trihydrate has the structure Template:Chem2.[3]
Preparation and reactions
Zirconium fluoride can be produced by several methods. Zirconium dioxide reacts with hydrogen fluoride and hydrofluoric acid to afford the anhydrous and monohydrates:
The reaction of Zr metal reacts at high temperatures with HF as well:
Zirconium dioxide reacts at 200 °C with solid ammonium bifluoride to give the heptafluorozirconate salt, which can be converted to the tetrafluoride at 500 °C:
Addition of hydrofluoric acid to solutions of zirconium nitrate precipitates solid monohydrate. Hydrates of zirconium tetrafluoride can be dehydrated by heating under a stream of hydrogen fluoride.
Zirconium fluoride can be purified by distillation or sublimation.[1]
Zirconium fluoride forms double salts with other fluorides. The most prominent is potassium hexafluorozirconate, formed by fusion of potassium fluoride and zirconium tetrafluoride:[4]
Applications
The major and perhaps only commercial application of zirconium fluoride is as a precursor to ZBLAN glasses.[1]
Mixture of sodium fluoride, zirconium fluoride, and uranium tetrafluoride (53-41-6 mol.%) was used as a coolant in the Aircraft Reactor Experiment. A mixture of lithium fluoride, beryllium fluoride, zirconium fluoride, and uranium-233 tetrafluoride was used in the Molten-Salt Reactor Experiment. (Uranium-233 is used in the thorium fuel cycle reactors.)Script error: No such module "Unsubst".
References
- ORNL/TM-2006/12 Assessment of Candidate Molten Salt Coolants for the Advanced High-Temperature Reactor (AHTR), March 2006 (Accessed 2008/9/18)