Study of growth kinetics in melt-textured YBa₂Cu₃O_7−x

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 YBa₂Cu₃O_7−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 t^1/3. Growth rate experiments were also conducted on these samples to determine the maximum growth rate for plane front solidification, R_max. This quantity was measured for undoped and doped Y-123, and it was found that the addition of Pt did not increase R_max 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.