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GENERATION AND CRITICAL EVALUATION OF THERMOCHEMICAL AND PHASE DIAGRAM DATAFOR HIGH-TC OXIDE SUPERCONDUCTORS - SUPERDATA

Objective

The purpose of the SUPERDATA project is:
-to provide information on the optimum thermochemical conditions for preparation of known (YBaCuO based) superconducting phases
-to define stability ranges of these phases as a function of process parameters
-to provide a basis for phase equilibrium calculations in other potential superconducting oxide systems.
The purpose of the SUPERDATA project is:
to provide information on the optimum thermochemical conditions for preparation of known (yttrium barium copper based) superconducting phases;
to define stability ranges of these phases as a function of process parameters; to provide a basis for phase equilibrium calculations in other potential superconducting oxide systems.

For this purpose experimental thermochemical methods as well as data assessments and ab initio calculations are employed.

The expected results are:
critically assessed and consistent thermochemical data for all relevant phases, ie Gibbs energy data as a function of composition and temperature;
a comprehensive specialised literature database for thermochemistry and phase diagrams.

Achievements to date involve the development of a literaturebase and the first data assessment for metallic subsystem yttrium barium copper oxide and metal oxide subsystems.

The phase relationships and the thermochemistry of the yttrium barium copper oxygen system were not known at the time of the discovery of the oxide superconductors by Bednorz and Mueller. Phase diagrams were available for only very few of the binary and ternary subsystems. Research has been carried out in order to provide a self consistent set of the Gibbs energies as function of temperature and, if applicable, composition for all phases of the system yttrium barium copper oxygen.

Experimental phase equilibria and thermochemical properties of the phases in the yttrium barium copper oxygen system taken from the literature have been augmented by crucial experiments involving calorimetry electromotive force (EMF) measurements, differential thermal analysis (DTA) and thermogravimetry (TG). For the superconductor phase (123) these experimental values have been supplemented by ab initio calculations of phase equilibria. Self consistent datasets for the subsystems barium copper, barium yttrium, copper yttrium, barium oxygen, copper oxygen, yttrium oxygen, barium copper yttrium, barium copper oxygen, barium yttrium oxygen, copper yttrium oxygen and the system yttrium barium copper oxygen with special emphasis on the solution range of the superconducting phase YBa2Cu3O6+x have been derived. With these data the standard types of phase diagram for the respective systems have been produced by way of equilibrium calculations. The data also have been applied successfully in the analysis of the thermochemical behaviour of a metallic 123-precursor and in the optimization of a chemical vapour deposition (CVD) process.
For this purpose experimental thermochemical methods as well as data assessments and ab initio calculations are employed.

The expected results are :
-critically assessed and consistent thermochemical data for all relevant phases, i.e. Gibbs energy data as a function of composition and temperature
-a comprehensive specialised literature database for thermochemistry and phase diagrams.

Coordinator

Rheinisch-Westfälische Technische Hochschule Aachen (RWTH)
Address
Kopernikusstraße 16
52074 Aachen
Germany

Participants (5)

INSTITUT NATIONAL POLYTECHNIQUE DE GRENOBLE
France
Address
Rue De La Piscine, 1130 - Domaine Universitaire De
38402 Saint-martin-d'heres
Kungliga Tekniska Hogskolan
Sweden
Address

10044 Stockhlom
Max-Planck-Institut für Festkorpforschung
Germany
Address
Heisenbergstraße 1
7000 Stuttgart
TECHNISCHE UNIVERSITAET CLAUSTHAL
Germany
Address
Adolph-roemer-strasse 2A
1253 Clausthal-zellerfeld
University of Sheffield
United Kingdom
Address
Hadfield Building Mappin Street
S1 3JD Sheffield