Growth of bulk Pr2-xCexCuO4+δ single crystals by B2O3 encapsulated flux technique

Growth of bulk single crystals of electron-doped superconductor Pr2-xCexCuO4+delta (Pr-214) by a novel B2O3 encapsulated flux technique is reported. Pr-214 crystals have been grown from both platinum and alunima crucibles. While using platinum crucible, flux-creeping problem was completely avoided and for alumina crucible the creeping was considerably reduced. A large surface area crystal of dimension 6 x 5 mm(2) was found to grow on the surface of the melt. Crystals of limited size (2 x 2 x 0.1 mm(3)) were observed within the cavities formed in the solidified mass. Observation of the grown crystals under SEM reveals a layer growth pattern, indicative of 2D nucleation mechanism. EDX analysis confirmed the stoichiometry of the grown crystals. No contamination was found in the crystals grown from platinum crucible and a trace amount of Al was detected in the crystals grown from alumina crucible. The segregation coefficient of Cc into the crystal is found to be 60%. Magnetization measurements reveal that the grown crystals are not superconducting even after nitrogen annealing at 900degreesC for 20 h, probably due to the difficulty in removing the oxygen in thick crystals. (C) 2002 Elsevier Science B.V. All rights reserved.