Formation and growth mechanisms of Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>y</sub> on an Ag substrate in the partial melting method
T Hasegawa; H Kobayashi; H Kumakura; K Togano; T Hasegawa; Showa Electr. Wire & Cable Co. Ltd., Kawasaki, Japan; H Kobayashi; Showa Electr. Wire & Cable Co. Ltd., Kawasaki, Japan; H Kumakura; Showa Electr. Wire & Cable Co. Ltd., Kawasaki, Japan; K Togano; Showa Electr. Wire & Cable Co. Ltd., Kawasaki, Japan
Журнал:
Superconductor Science and Technology
Дата:
1994-08-01
Аннотация:
We investigated the phase changes of a Bi-Sr-Ca-Cu-O/Ag composite tape during cooling from a partially molten state using the high-temperature X-ray-diffraction and oil-quenching techniques. In the cooling process, (SrCa)CuO<sub>2</sub> and Bi(SrCa)<sub>2</sub>O<sub>y</sub> appeared at the areas where the (SrCa)<sub>2</sub>CuO<sub>3</sub> phase disappeared. At around 860 degrees C, these solid phases melted into the liquid phase, and then Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>y</sub> (Bi-2212) grew rapidly at the surface. First, nucleation of Bi-2212 occurred at the surface of the liquid phase. With decreasing temperature the Bi-2212 crystal growth proceeded slowly from the surface to the inner area with the a-b plane almost parallel to the surface. During the growth of Bi-2212, excess Bi was ejected from Bi-2212 and a thin Bi-enriched layer was formed at the growth front of Bi-2212.
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