Hydrolysis Reactions at the Surface of Fluorozirconate Glass

The surface reaction products associated with the hydrolysis of ZBLA glasses have been characterized using X‐ray photoelectron spectroscopy. The predominant surface reaction product in water and basic solutions is a zirconium (hydr)oxy‐fluoride species. The compositional analyses indicate that the (hydr)oxyfluoride which forms in water has an average oxygen‐to‐fluorine ratio of ∼2/5. The Zr 3d binding energy of this (hydr)oxyfluoride species was interpreted on the basis of its Pauling charge; this verified the compositional analyses and suggested a seven‐coordinate surface species of the form ZrO₂F₅ or Zr(OH)₂F₅. It is proposed that zirconium (hydr)oxyfluoride is created in all aqueous solutions because of attack of Zr–F bonds by molecular water. The extent of reaction in water influences the surface concentration of the oxyfluoride species, but not their composition. In very acidic solutions, the surface concentration of (hydr)oxyfluoride is minimal, whereas in highly basic solutions the (hydr)oxy‐fluoride species exhibits an increased oxygen‐to‐fluorine ratio.