Superconducting properties and microstructure of PLD-ErBa ₂Cu₃O_7-δ films with BaNb ₂O₆

We report superconducting properties and microstructures of ErBa ₂Cu₃O_7-δ (ErBCO) films with BaNb ₂O₆ (BNO) grown by Pulsed Laser Deposition (PLD) on SrTiO₃ (STO) substrates. The BNO was introduced into the ErBCO films as an artificial pinning center. X-ray diffraction analysis indicated the high orientation both c-axis and in-plane for the obtained ErBCO films. An ErBCO film with BNO-doping (BNO + ErBCO) maintained the high critical temperature (T _C) comparison with an ErBCO film with BZO-doping (BZO + ErBCO). Nanorods were observed clearly in Transmission Electron Microscopy (TEM) images of the BNO+ErBCO films. The nanorod diameter was smaller with lower substrate temperature during deposition. The BNO + ErBCO films showed higher critical current density (J_C) than that of a pure ErBCO film for field//c-axis. Furthermore, we confirmed a tendency that J_C of the BNO+ErBCO films were enhanced with lower substrate temperature. This indicates that nanorods observed in cross-sectional TEM images affected as c-axis correlated pinning centers. We suggest that the BNO is effective as a pinning material for ErBCO film with maintaining high T_C.