Thermodynamic calculation of yttrium-barium-copper-oxygen
International Science Foundation Long-Term Research Grants Program
- Principal Investigator Name and Address
- Gennady Fedorovich Voronin
Moscow State University
- V.A. Lysenko
Grant Number MRL 000
In 1994, the new results as follows below have been obtained in
accordance with the plan of the project:
- The subsolidus equilibria in the mixture
yttrium-barium-copper-oxygen including the metastable states of
superconductor phases have been computed.
Fig. 1. Stability fields of the 123 phase.
This phase is thermodynamically stable between the bold lines 1-5. The
lines 1-7 represent decomposition reactions according to equations
- The phase equilibria and thermodynamic values for the subsystems of
copper-yttrium, barium-yttrium, copper-barium-yttrium, yttrium-oxygen
including all the intermediate phases, solid and liquid solutions have
been evaluated ("optimized").
Fig 2. Solidus and liquidus of Y-O system.
Fig. 3. Phase diagram of
Fig. 4. Phase diagram
of the Cu-Y.
Fig. 5. Phase diagram of
the Ba-Cu-Y at 1273 K.
- The method for estimating thermodynamic functions in homologous
series of compounds have been developed and, after that, the
thermodynamic properties of the hypothetical high temperature
superconductors, Y2Ba4Cu9O17 and YBa2Cu5O9 have been estimated. From
here, the conditions (temperature, oxygen pressure and composition) when
these two phases can be synthesized have been predicted.
Fig. 6. Phase diagram of the system
YBa2Cu3O6+z + CuO at 1 atm of oxygen pressure
- The thermodynamic models and auxiliary values to calculate other
subsystems and the complete quaternary yttrium-barium-copper-oxygen
system have been prepared.