Atom-replaced pins in a Y-based superconductor—single-crystalline perovskite structure including both PrBa2Cu3O7−x and YBa2Cu3O7−y

Metal Organic Deposition using Trifluoroacetates (TFA-MOD) provides many uniform superconductors on long metal tapes. The large numbers of long wires have been applied for power grids or superconducting fault current limiters. The related applications work for a long time without fatal trouble. The quasi-liquid during the firing process assists the perfectly uniform structure in TFA-MOD. On the other hand, however, when it is desired to introduce artificial pinning centers, the quasi-liquid also enlarges the diameter of the artificial pinning centers to several tens of nanometers. In other words, due to the nature of TFA-MOD, there is virtually little possibility of using TFA-MOD to prepare several nm-sized artificial pinning centers. By proposing Atom-Replaced Pins (ARPs), we want to overcome the impasse. ARP is realized by replacing yttrium (Y) with praseodymium (Pr) whose valence number changes from 3+ to approximately 4+. Analytical results suggested that Pr makes pinning centers on PrBalsubg2l/subgCulsubg3l/subgOlsubg7-xl/subg (PrBCO) unit cell, and the weak-linked superconductivity derived from PrBCO extends to the adjacent unit cells in liga/bl/ig-plane. ligJl/iglsubgcl/subg decrease by Pr is five times as large as the volume fraction of Pr in the Y-site of the perovskite structure. On the other hand, ligTl/iglsubgcl/subg does not show large degradation in YBCO including 10% PrBCO. These results suggest that PrBCO unit cells are fully dispersed in YBalsubg2l/subgCulsubg3l/subgOlsubg7-yl/subg matrix. With regard to Jc in the magnetic field, (Ylsubg0.98l/subg, Prlsubg0.02l/subg)BCO has been slightly improved compared with pure YBCO only in the region of high temperature and low magnetic field of less than 1 T.