ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The growth behaviour of Y1Ba2Cu3O7−δ(Y1-2-3) crystals has been studied by horizontal directional solidification of samples heated into the liquid (L) plus Y2Ba1Cu1O5(Y2-1-1) phase field. Cylindrical samples of initially stoichiometric Y1-2-3 composition were solidified at rates ranging from 1 to 10 mm h−1 using temperature gradients between 2.5 and 5 K mm−1. A novel method was employed to support the L+Y2-1-1 semi-solid and minimize reaction with the crucible. Selected samples were quenched during solidification so that growth mechanisms could be studied. Quasi-single crystals of Y1-2-3 formed, providing that the growth rate did not exceed 1 mm h−1 and that the temperature gradient was 〉 3.5 K mm−1. The quasi-single crystals contained particles of Y2-1-1 as well as Ba-Cu-rich bands as secondary phases and had a preferred orientation of [001] at 45° to the growth axis when grown from a polycrystalline seed crystal. No preferred orientation developed when samples were grown without a seed. In quenched samples, macroscopic growth steps were observed on the (001) plane, and within the cylindrical sample the faces of the growing crystal were found to be mutually perpendicular planes. During solidification liquid was found to be lost from the L+Y2-1-1 semi-solid region of the sample. This occurred both by wetting of the support bars and by liquid migration into the seed crystal region.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01154492
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