Bulk High Temperature Superconductors for High Field Apps

Tweet Professor Cardwell recently discussed the bulk microstructure of YBCO, and explained the effect of second-phase inclusions on the flux-pinning capability of the material. Methods had now been developed to incorporate nano-scale inclusions into the bulk structure, and a 10-200nm nano-phase based on RE2Ba4CuMOy had been shown to form effective artificial flux-pinning sites. Although these materials required further refinement in microstructural homogeneity, they appeared extremely promising for improved critical-current-density bulk superconductors.

• Bulk , large grain (RE)BCO HTS have significant potential for high field applications.
• A new nano-phase (10-200 nm) has been developed based on RE2Ba4CuMOy that forms effective flux pinning sites in bulk HTS.
• The 2411 phase does not coarsen at high temperatures or contaminate the RE-123 phase.

Applications of Bulk Superconductors
1. Magnetic bearing
- Low loss
- Flywheel energy storage
2. Motors and generators
- Higher efficiency, lower loss, smaller machines
3. NMR imagers
- DC field source, pre-polarisation
4. Other applications

Some Fields
Earth’s field 0.0001 T
Solenoid 0.1 T
Permanent magnet (iron) 1.5 T
(SmCo) 0.8 T
LTS MTI magnets 5 T

Record Trapped Fields
Temperature Trapped Flux Lab.
(K) (T)
77 2.2# ISTEC
77 3.2 Houston (2 samples)
65 5.3 Houston (2 samples)
47 11.2* Dresden
29 17.0# ISTEC

# Epoxy encapsulated * Steel banded
Explosive flux compression 2,500 T
43 Page presentation pdf

Material Options for Bulk HTS Magnets
Only one class of material suitable for applications at 77 K;

Large, grain boundary-free (RE)BCO

Processed in the form of large single grains by a variety of melt processing techniques