The critical current density and trapped field of large grain RE123 bulk superconductors have drastically increased in the last few years. High-quality bulk superconducting magnets can trap a very high magnetic field of 3T at 77K and above 15T at 20K. The recent progress in bulk superconducting materials has led to many applications such as superconducting flywheel systems, current leads, superconducting motors, magnetic separation systems, magnetron sputtering machines. In this paper, we review recent research and development of the processing, critical current density, trapped field and mechanical properties of melt-textured bulk superconducting materials.
Large-grain RE (rare earth elements)-Ba-Cu-O bulk superconductors have potential trapping magnetic fields greater than 5T at liquid-nitrogen temperature. However, cracks are easily formed in large bulk samples due to their poor mechanical properties. Thus, the maximum trapped magnetic field is restricted by the mechanical properties rather than superconducting properties. It is therefore important to seek techniques to enhance the mechanical properties. In this review, I summarize the present status of investigations regarding the mechanical properties for melt-processed RE-Ba-Cu-O bulk superconductors.
In this review we summarize the present status of resin impregnation techniques for bulk high-temperature superconductors. Epoxy resin can permeate into the interior of bulk RE (rare earth element)-Ba-Cu-O superconductors when they are immersed in molten resin. Mechanical properties of resin-impregnated bulk RE-Ba-Cu-O are dramatically enhanced in addition to the enhancement of corrosion resistance. The thermal expansion coefficient can be controlled by adding quartz fillers to epoxy. Wrapping the bulk superconductors with carbon fabric prior to resin impregnation is effective in further enhancing the mechanical properties. Resin-impregnated bulk RE-Ba-Cu-O materials have already been employed for several practical applications.