Phase equilibria among the superconductors in the Y2O3-BaO-Cu-O system

Zhigang Zhou, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The enthalpy of formation of Y2Ba4Cu7O14.864 at room temperature has been determined by using high-temperature reaction calorimetry. The standard enthalpy of formation of the 247 phase is ΔH°f = -5463±18 kJ mol-1. Phase relationships among the superconductors, namely, the 123, 124, and 247, are assessed. It is intrinsic that impurity phases, such as Y2Cu2O5, BaCuO2, CuO, etc., coexist with the superconductors at equilibrium. Equilibria among the superconductor phases in the Y2O3-BaO-Cu-O system have been determined. The results show that, at the 124 bulk composition, the 247 phase coexists with the excess CuO in a narrow area of pO(2) to approximately T space confined by the stability fields of the 124 phase and a mixture of the 123+CuO. The standard free energies of carbonation and hydration of the 247 phase are also determined, which are -629±13 kJ mol-1 and -873±45 kJ mol-1, respectively. Like the 123 and 124 phases, the 247 phase is thermodynamically unstable for corrosion by water vapor and carbon dioxide in ambient atmosphere.

Original languageEnglish (US)
Pages (from-to)3511-3517
Number of pages7
JournalJournal of Materials Research
Issue number9
StatePublished - Sep 1999
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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