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Effect of grain alignment and processing temperature on critical currents in YBa2Cu3O7-δ sintered compacts

Published online by Cambridge University Press:  31 January 2011

J. E. Tkaczyk
Affiliation:
General Electric Corporate Research and Development, Schenectady, New York 12301
K. W. Lay
Affiliation:
General Electric Corporate Research and Development, Schenectady, New York 12301
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Abstract

Magnetically aligned YBa2Cu3O7-δ ceramics show resistivities approaching that of single crystals and improved transport critical currents in a magnetic field. Reduced microcracking and increased transport along the ab-plane are believed responsible for the improved performance over nonaligned ceramics. Aligned and nonaligned samples were prepared in parallel using a range of sintering and annealing temperatures. A rapid rise in density for samples sintered above 900°C in oxygen is accompanied by rapid grain growth, improved alignment, a drop in the room temperature resistivity, and an increase in the critical current. The presence of low melting point (i.e., Ba–Cu–O-rich) phases at grain boundaries is believed responsible for the rapid densification. However, the presence of this phase does not appear to be the most important factor limiting Jc. A high temperature oxygen anneal at 900°C improved performance as compared to anneals at 500°C, possibly due to the removal of carbon. For aligned samples sintered at 980°C, critical currents are over 200 A/cm2 at 77 K, ¼ tesla, and room temperature resistivities are below 350 μΩ-cm.

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Copyright
Copyright © Materials Research Society 1990

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