The microstructure within single domains of melt-processed ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ (1:2:3) material has been examined. Rather than composing a ‘‘brick-wall’’ structure, the stacked, parallel platelets within the domains are actually portions of a single crystal. A growth mechanism is proposed that is consistent with the observed microstructural features. The anisotropic nature of the growth of 1:2:3 results in gaps separating the platelets. The gaps, however, terminate within domains, resulting in interconnected single-crystalline material. The absence of weak-link behavior for current flow along the c axis and the high critical-current densities observed within domains of melt-processed 1:2:3 material are readily explained by the fact that current flow is solely through single-crystalline material.

• Received 30 September 1991

DOI:https://doi.org/10.1103/PhysRevB.45.5622