Thermodynamically controlled melt processing to improve bulk materials

High quality melt textured YBCO samples have been prepared on a modified MTG route. A trapped magnetic field of 8.5 T at 51.5 K was measured in the gap of 1 mm in a mini-magnet from two YBCO cylinders (d=26 mm, h=12 mm). At 77 K, each single domain cylinder traps more than 600 mT and the levitation pressure of 15 N/cm/sup 2/ in a distance of 0.5 mm was achieved by a 0.4 T SmCo magnet. The thermodynamic background of the preparation method is outlined. A thermodynamic approach to control growth and stoichiometry y in the alternative material Nd/sub 1+y/Ba/sub 2-y/Cu/sub 3/O/sub x/ is discussed. Critical currents of 46 kA/cm/sup 2/ (77 K) have been achieved by a modified recipe.