GROWTH AND POSSIBLE SIZE LIMITATION OF QUALITY SINGLE-GRAIN YBA2CU3O7

We have studied the growth of disks of single-grain YBa2Cu3O7 (YBCO) w ith diameter to 5 cm using a top-seeded melt-texture technique. The qu ality of these YBCO disks was found to depend critically on the qualit y and size of the seed used, the temperature schedule of the growth ad opted, the amount of Y2BaCuO5 and Pt added, and the size of the final disks processed. Samples of a diameter of 2.5 cm so-prepared have been observed to shield a magnetic field greater than 20 T at 4.2 K and to trap a field of 1.3 T at 77 K. However, no significant increase in th e trapped field has been achieved by increasing the diameter of the di sk to beyond approximately 3 cm.