Abstract
Oxide-superconductor bulk materials that can act as magnets after field cooling were made by a modified quench-and-melt-growth (QMG) process. To enlarge QMG crystals having a fine 211 phase in the matrix of a crystalline 123 phase, a modi tied QMG process was developed by adding a seeding technique and a Pt addition technique to the original QMG process. Enlarged QMG bulk superconductors were operated as high-field permanent magnets. A bulk magnet 70 mm in diameter and 35 mm in thickness had trapped maximum values of 4.5 T, 2.5 T, and 0.99 T at 40 K, 63 K, and 77 K, respectively. Thermornagnetomechanical instability leading to quenching phenomena was not observed above 40 K.
