Y distribution in Ba-Cu-O melt during growth of superconducting material Y123 by Czochralski method
by
Janusz Szmyd
Department of Theoretical Metallurgy and Metallurgical Engineering, University of Mining and Metallurgy, 30-059 Krakow, Poland,
Coauthors: K. Gajek, K. Suzuki

Since discovery in 1987 of superconductivity at ~90 K in a new mixed-phase compound system, an enormous amount of attention has been given to the improvement of the quality of these materials. One of the most seriously studied compounds is the yttrium barium copper oxide superconductor YBa2Cu3O7-x (Y123). In 1993 continuous growth of Y123 large single crystals was achieved by applying a modification of the Czochralski method. The quality of yttrium barium copper oxide superconductor Y123 crystals grown from a melt by this method is significantly affected by heat and mass transfer in the melt during growth. In an Y123 single crystal growth system the Y123 single crystal grows directly from the liquid phase as a primary phase by the migra tion of Y atoms from the solute Y2BaCuO5 (Y211) on the bottom of the melt to the free surface. The Y123 crystal grows continuously as long as the nutrient Y211 exists. In this method, convection in the melt is an important factor in controlling distributi on of Y atoms in the melt, due to the high Schmidt number of the melt (Sc = 7000).

This paper describes transport phenomena during growth of superconducting materials and presents the numerical computations of the flow, thermal and Y concentration fields in the melt for Y123 single crystal growth by this modified method. The flow in th e melt was modelled as an incompressible, Newtonian and Boussinesque fluid. Calculations are presented for a combination of buoyancy - driven flow and flow driven by crystal rotation.

Date received: April 21, 1999

Copyright © 1999 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caco-34.