Abstract
We investigated the macroscopic and microscopic critical current densities of a melt processed materials by a magnetic measurement. By the Quench and Melt Growth (QMG) process, large YBa2Cu3Ox crystals without a large angle grain boundary can be obtained. Several types of powders less than 100ωm were prepared by pulverizing and classifying QMG crystals. These powders were aligned in a magnetic field and the magnetization was measured. The magnetization hysteresis of the prepared powders was proportional to their average diameter. The critical current density of the powders estimated from the Bean model is higher than that of the bulk crystal. This indicates that the current in the grain is not uniform. A current is probably prevented by cracks mostly parallel to the ab-plane or subgrain boundaries.
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