Fabrication of NdBa2Cu3O7-δ single crystals by the top-seeded solution-growth method in 1%, 21%, and 100% oxygen partial pressure atmosphere

Single crystals of NdBa2Cu3O7-δ (Nd123) have been successfully grown by the top-seeded solution-growth (TSSG) method in 1%, 21% and 100% oxygen partial pressure atmosphere ((P(O2) = 0.01 atm, P(O2) = 0.21 atm and P(O2) = 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 between the molten solvent and the Nd2O3 crucible. Compositions of Nd123 single crystals grown in different oxygen partial pressure atmospheres were 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(O2) = 0.01 atm, Nd:Ba:Cu = 1.07:1.95:3.00 for P(O2) = 0.21 atm and Nd:Ba:Cu = = 1.10:1.90:3.00 for P(O2) = 1.00 atm, respectively. The Nd123 single crystals grown in different oxygen partial pressure atmospheres were annealed in a pure oxygen gas flow, and the temperature dependence of the DC magnetization for these crystals was measured using a superconducting quantum interference device (SQUID) magnetometer. The Nd123 single crystal grown in P(O2) = 0.01 atm, and annealed at 340°C for 200 h showed a steep superconductive transition at 96 K. On the other hand, the Nd123 crystal grown in P(O2) = 0.21, 1.00 atm and, annealed at 340°C for 200 h exhibited a broad transition at 92 K for P(O2) = 0.21 atm and at 88 K for P(O2) = 1.00 atm, respectively. Therefore for Nd123 single crystal production with high quality superconductive characteristics, a low oxygen partial pressure atmosphere during crystal growth is found to be effective for minimizing the substitution Nd ions into Ba sites.