Single Crystal Growth of 123 YBCO and 2122-BCSCO Superconductors

Abstract

Single crystals of 2021-phase (Tc .apprxeq. 10 K, c .apprxeq. 24 .ANG.) and 2122-phase (Tc .apprxeq. 80 K, c .apprxeq. 30 .ANG.) in the Bi Ca Sr Cu oxide family have been grown successfully using KCl flux by the temp. gradient transport method. This technique allows one to grow large crystals by employing the optimized conditions of cooling range, charge compn., etc. This paper also discusses the usefulness of KCl.KF flux for the growth of BCSCO crystals. Pb-doped charges were used for the growth of 110 K phase, but it was not possible to grow this phase as single crystals. It may be possible to synthesize crystals of Bi2Ca2Sr2Cu3Ox phase with c .apprxeq. 37 .ANG. and Tc .apprxeq. 110 K if the crystn. range and the suitable starting compns. without Pb can be optimized. Also, relatively large and free standing crystals of YBa2Cu3O6.5+x have been synthesized using BaO.CuO flux by slow cooling the melt in a split crucible configuration. This modification may be utilized to grow larger crystals of YBaCu-oxide. The problem encountered with harvesting crystals is easily solved by using the split crucible configuration.