a1 Texas Center for Superconductivity and Department of Mechanical Engineering, University of Houston, Houston, Texas 77204
a2 Intermagnetics General Corporation, Latham, New York
a3 Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
a4 Texas Center for Superconductivity and Department of Mechanical Engineering, University of Houston, Houston, Texas 77204
Directional solidification has been shown to be a successful way of achieving high current densities in bulk YBCO. The lack of understanding of the growth kinetics, however, makes it difficult to fabricate longer samples and reduce the processing times. To study the growth kinetics, quenching experiments of undoped YBa2Cu3O7−x (Y-123) and Y-123 doped with Pt and Nd from above the peritectic temperature with different holding times, t, were conducted. The results of these experiments indicate that the average 211 particle size varies at t1/3. Growth rate experiments were also conducted on these samples to determine the maximum growth rate for plane front solidification, Rmax. This quantity was measured for undoped and doped Y-123, and it was found that the addition of Pt did not increase Rmax while the addition of Nd doubled the growth rate. Using the coarsening results together with the growth rate experiments, the diffusivity of Y in liquid and the 211-liquid interfacial energy for undoped and doped Y-123 were calculated.
(Received December 04 1995)
(Accepted June 04 1996)