Fabrication of large-grain bulk superconductors in microgravity environment

The experiment to fabricate large-grain RE-Ba-Cu-O (RE: Rare-Earth element) bulk superconductors in microgravity environment will be performed in the Unmanned Space Experiment Recovery System project. It is difficult to grow high-quality large-grain superconductors on the ground due to the chemical contamination from the substrate and the segregation of liquid phase. Such problems can be overcome by growing large RE-Ba-Cu-O bulk in microgravity environment, in which the bulk can be supported by a seed crystal alone during the crystal growth. In this paper, we describe the experiment plan, the materials composition, design of a temperature gradient furnace and the conditions for the crystal growth.