Evgenii B. Rudnyi

Thermodynamic Assessment of the Ba-Cu-Y System

Objective

Complete phase diagram of the Ba-Cu-Y system which is a part of the famous Y-Ba-Cu-O system containing high temperature superconductor phases and may have applications as a metallic precursor for producing superconductors.

Means

Combined processing of all the experimental values available and thermodynamic modeling.

Result

Thermodynamic functions of all the phases in the Ba-Cu-Y system that allow us to draw the complete phase diagram.

Abstract

• The literature experimental values pertaining to thermodynamics of the Ba-Cu-Y system have been collected:
  • stoichiometry of compounds
  • thermal analysis,
  • phase equilibria,
  • drop calorimetry,
  • enthalpy of mixing.
• The thermodynamic models of all the phases have been chosen and the Gibbs energies have been estimated after combined processing of the experimental values.
• A program to compute the equilibrium composition in the Ba-Cu-Y system in the temperature range from 400 to 4000 K from the estimated Gibbs energies has been written.

Design

1. Optimizing the Ba-Cu system

   Given: the experimental liquidus and non-variant temperatures, the partial enthalpies of the melt, and the enthalpy of formation of BaCu.

   Obtained: the Gibbs energies of stoichiometric phases BaCu and BaCu13, and of the liquid alloys Ba-Cu.

2. Optimizing the Cu-Y system

   Given: the experimental liquidus and non-variant temperatures, the enthalpies of the mixing of the melt, the HT-H298 values for eight compositions of the system and the enthalpy of formation of CuY.

   Obtained:the Gibbs energies of stoichiometric phases Cu6Y, Cu4Y, Cu7Y2, Cu2Y, and CuY, and of the liquid alloys Cu-Y.

3. Optimizing the Ba-Cu-Y miscibility gap

   Given: the experimental tie-lines for miscibility gap, the Gibbs energies of the binary melts Ba-Cu and Cu-Y.

   Obtained: the Gibbs energy of the liquid alloys Ba-Cu-Y.

Slides

• THERMODYNAMIC MODELS
• EXAMPLE: Optimizing the Ba-Cu system
• FEATURE: Statistical Model of Systematic Errors
• Thermodynamics of Ba-Cu (H, Ai in J/mol, S, Bi in J/K/mol)
• Thermodynamics of Cu-Y (H, Ai in J/mol, S, Bi, Ci in J/K/mol)
• OPTIMIZING MISCIBILITY GAP
• COMPUTING PHASE DIAGRAM: DO Non-Linear Programming (DONLP)
• COMPARISON

Plots

• Phase diagram of the Ba-Cu
• Partial enthalpies of the liquid Ba-Cu alloys
• Gibbs energy of mixing of the liquid Ba-Cu alloys
• Phase diagram of the Cu-Y
• The integral enthalpies of the liquid Cu-Y alloys
• HT-H298 values for eight compositions of the Cu-Y system
• Gibbs energy of mixing of the liquid Cu-Y alloys
• Miscibility gap in the Ba-Cu-Y at 1273 K
• Miscibility gap in the Ba-Y system
• Heating curve for 0.337 Ba + 0.496 Cu +0.167 Y
• Heating curve for 0.219 Ba + 0.679 Cu +0.102 Y
• Heating curve for 0.100 Ba + 0.845 Cu +0.055 Y

Papers with links to sofware

E. B. Rudnyi.
Thermodynamic assessment of the Ba-Cu system.
Zh. Fiz. Khim. 1996, v. 70, N 6, p. 986-990 (in Russian). Russ. J. Phys. Chem. (English transl.), 1996, v. 70, N 6.
Preprint or reprint in Russian, data and code in varcomp and in tdlib.

E. B. Rudnyi.
Thermodynamic assessment of the Cu-Y system.
Zh. Fiz. Khim. 1996, v. 70, N 6, p. 1007-1011 (in Russian). Russ. J. Phys. Chem. (English transl.), 1996, v. 70, N 6.
Preprint or reprint in Russian, data and code in varcomp.

E. B. Rudnyi, G. F. Voronin.
Thermodynamic assessment of the ternary Ba-Cu-Y system. Direct optimization of the miscibility gap.
CALPHAD, 1996, v. 20, N 3, p. 297-305.
Preprint, final paper at ScienceDirect, software bacuy_eq, varcomp.

E. B. Rudnyi.
Statistical model of systematic errors: An assessment of the Ba-Cu and Cu-Y phase diagram.
Chemometrics and Intelligent Laboratory Systems, 1997, v. 36, p. 213-227.
Preprint, final paper at ScienceDirect, data and code in varcomp, for Ba-Cu also in tdlib.