FABRICATION OF NDBA2CU3O7-DELTA SINGLE-CRYSTALS BY THE TOP-SEEDED SOLUTION-GROWTH METHOD IN 1-PERCENT, 21-PERCENT, AND 100-PERCENT OXYGEN PARTIAL-PRESSURE ATMOSPHERE

Single crystals of NdBa2Cu3O7-delta (Nd123) have been successfully gro wn by the top-seeded solution-growth (TSSG) method in 1%, 21% and 100% oxygen partial pressure atmosphere ((P(O-2) = 0.01 atm, P(O-2)= 0.21 atm and P(O-2) = 1.00 atm). Ba-Cu-O solvent with a Ba to Cu ratio of 3 :5 was used in a Nd2O3 crucible. Nd is supplied by the reaction betwee n the molten solvent and the Nd2O3 crucible. Compositions of Nd123 sin gle crystals grown in different oxygen partial pressure atmospheres we re analyzed by inductivity coupled plasma atomic emission spectrometry (ICP-AES) and confirmed to be Nd:Ba:Cu = 1.01:1.97:3.00 for P(O-2) = 0.01 atm, Nd:Ba:Cu = 1.07:1.95:3.00 for P(O-2) = 0.21 atm and Nd:Ba:Cu = = 1.10:1.90:3.00 for P(O-2) = 1.00 atm, respectively. The Nd123 sin gle crystals grown in different oxygen partial. pressure atmospheres w ere annealed in a pure oxygen gas flow, and the temperature dependence of the DC magnetization for these crystals was measured using a super conducting quantum interference device (SQUID) magnetometer. The Nd123 single crystal grown in P(O-2) = 0.01 atm, and annealed at 340 degree s C for 200 h showed a steep superconductive transition at 96 K. On th e other hand, the Nd123 crystal grown in P(O-2) = 0.21, 1.00 atm and, annealed at 340 degrees C for 200 h exhibited a broad transition at 92 K for P(O-2) = 0.21 atm and at 88 K for P(O-2) = 1.00 atm, respective ly. Therefore for Nd123 single crystal production with high quality su perconductive characteristics, a low oxygen partial pressure atmospher e during crystal growth is found to be effective for minimizing the su bstitution of Nd ions into Ba sites.