A NONPOLLUTING SINGLE-CRYSTAL GROWTH-PROCESS FOR YBACUO AND PHASE-DIAGRAM STUDIES

A new method of growing single crystals of YBa2Cu3O6 + x is presented which uses an Y2O3 crucible containing a composition close to the binary eutectic BaO-CuO. Large crystals are obtained which may be homogeneised by a subsequent oxygen treatment (superconducting transition at 88 K, 2 K wide). The phase diagram of the subsystem Y2BaCuO5-BaCuO2-CuO centered on the 123 compound was investigated. The composition of two peritectic points corresponding to the reactions YBa2Cu3O6 + x → Y2BaCuO5 + L and YBa2Cu3O6 + x + CuO → Y2BaCuO5 + L were determined and the boundaries of the primary crystallization field of the YBa2Cu3O6 + x phase was precised. These results allowed to optimize the crystal growth parameters. © 1990.