The thermodynamics of formation, molar heat capacity, and thermodynamic functions of ZrTiO4(cr)

Benjamin K. Hom, Rebecca Stevens, Brian F. Woodfield, Juliana Boerio-Goates, Robert L. Putnam, Katherine B. Helean, Alexandra Navrotsky, Robert L. Putnam

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

As part of an ongoing study of titanate-based ceramic materials for the disposal of surplus weapons-grade plutonium, we report thermodynamic properties of a sample of zirconium titanate (ZrTiO4) quenched from a high-temperature synthesis. The standard enthalpy of formation ΔfHmo was obtained by using high-temperature oxide-melt solution calorimetry. The molar heat capacity Cp, m was measured from T = 13 K to T = 400 K in an adiabatic calorimeter and extrapolated to T = 1800 K by using an equation fitted to the low-D temperature results. The results at T = 298.15 K are ΔfHmo = -(2024.1 ± 4.5) kJ·mol−1, ΔOTSmo = (116.71 ± 0.31) J·K−1·mol−1, and ΔfGmo = -(1915.8 ± 4.5) kJ·mol−1; the molar entropy includes a contribution of 2Rln 2 to account for the random mixing of Zr4+ and Ti4+ on a four-fold crystallographic site. Values for the standard molar Gibbs energies and enthalpies of formation of ZrTiO4; ΔfGmo and ΔfHmo, and for the free energies and enthalpies for the reaction to form ZrTiO4(cr) from ZrO2(cr) and TiO2(cr), are tabulated over the temperature interval, 0 ≤ (T /K) ≤ 1800. From these results, we conclude that ZrTiO4 is not stable with respect to (ZrO2 + TiO2) at T = 298.15 K, but becomes so at T = (1250 ± 150) K.

Original languageEnglish (US)
Pages (from-to)165-178
Number of pages14
JournalJournal of Chemical Thermodynamics
Volume33
Issue number2
DOIs
StatePublished - 2001
Externally publishedYes

Keywords

  • Enthalpy
  • Enthalpy of formation
  • Entropy
  • Heat capacity
  • Thermodynamics
  • ZrTiO

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Physical and Theoretical Chemistry

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