High-temperature calorimetric study of glass-forming fluorozirconates

I. Ching Lin, Alexandra Navrotsky, John Ballato, Richard E. Riman

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Using high temperature calorimetric techniques, enthalpies of mixing of melts, enthalpies of formation of glasses and enthalpies of formation of crystals have been measured in binary systems ZrF4-BaF2, ZrF4-NaF, ZrF4-LaF3 and selected compositions in the system ZrF4-BaF2-LaF3-AlF3-NaF. The system ZrF4-LaF3 shows essentially zero enthalpies of mixing of melts. In the other systems, there are strongly exothermic enthalpies of mixing. In the binary systems ZrF4-BaF2 and ZrF4-NaF, the enthalpy of mixing of melts and the enthalpy of formation of crystals show minima at the same compositions, Ba2ZrF8 and Na3ZrF7, respectively, indicating the stoichiometric complexes ZrF4-8 and ZrF3-7. These results are discussed in relation to energetics, structure, speciation and acid-base chemistry and suggest the following: ZrF4, LaF3 and AlF3 are anionic complex-formers, while BaF2 and NaF are ionized in the molten state. The coordination number of the zirconium fluoride anionic complex varies with the amount of alkali or alkaline earth fluoride. A model is proposed in which glass-forming melts are dominated by ZrF-5 species and lie near deep eutectics. Therefore, glass formation in fluorozirconates involves a substantial structural change, which is dominated by short-range atomic arrangements, from the melt with predominantly ZrF-5 to the glass where zirconium is 7 or 8 coordinated by fluorine.

Original languageEnglish (US)
Pages (from-to)113-124
Number of pages12
JournalJournal of Non-Crystalline Solids
Issue number2-3
StatePublished - Jul 1997
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Materials Chemistry


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