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Journal of Materials Science

, Volume 26, Issue 12, pp 3374-3379

Standard Gibbs' energies of formation of BaCuO2, Y2Cu2O5 and Y2BaCuO5

  • A. M. AzadAffiliated withMetallurgy Division, Indira Gandhi Centre for Atomic Research
  • , O. M. SreedharanAffiliated withMetallurgy Division, Indira Gandhi Centre for Atomic Research
  • , K. T. JacobAffiliated withDepartment of Metallurgy, Indian Institute of Science

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Abstract

The Gibbs' energies of formation of BaCuO2, Y2Cu2O5 and Y2BaCuO5 from component oxides have been measured using solid state galvanic cells incorporating CaF2 as the solid electrolyte under pure oxygen at a pressure of 1.01×105 Pa 〈BaO〉 + 〈CuO〉 → 〈BaCuO2〉 ΔG f,ox o (± 0.3) (kJ mol−1)=−63.4−0.0525T(K) 〈Y2O3〉 + 2〈CuO〉 → 〈Y2Cu2O2〉 ΔG f,ox o (± 0.3) (kJ mol−1)=18.47−0.0219T(K) 〈Y2O3〉 + 〈BaO〉 + 〈CuO〉 → 〈Y2BaCuO5〉 ΔG f,ox o (± 0.7) (kJ mol−1)=−72.5−0.0793T(K) Because the superconducting compound YBa2Cu3O7−δ coexists with any two of the phases CuO, BaCuO2 and Y2BaCuO5, the data on BaCuO2 and Y2BaCuO5 obtained in this study provide the basis for the evaluation of the Gibbs' energy of formation of the 1-2-3 compound at high temperatures.