YBCO bulk superconductors prepared by top-seed PMP process

Top-seeded powder melting process (TSPMP) is an effective melting processing technique for the preparation of high J_c bulk YBCO. The remarkable advantage of TSPMP is that it is very convenient to control the size and distribution of 211 particles within bulk YBCO. We observed the microstructure of TSPMP-YBCO sample and the mean size of 211 particles is about 500 nm and well distributed. The thickness of 123 planes is about 2 μm. The density of twins in line is about (1.2-1.6)×10⁴ cm^-1. We fabricated the YBCO bulk sample with dimensions of ∅30mm×15 mm in batch by the TSPMP process. The maximum levitation force was measured to be 85 N at 77 K in 0.5 T, by using ∅28mm×30 mm NdFeB magnet.