Influence of YBa2HfO5.5 - 'derived secondary phase' on the critical current density and flux-Pinning force of YBa2Cu3O7-delta thick. films

摘要

Enhancement in critical current density (J(c)) and flux pinning force (F-p) in superconducting thick films of YBa2Cu3O7-delta (YBCO) added with small quantities of nanopowders of HfO2, BaHfO3 and YBa2HfO5.5, coated on YBa2ZrO5.5 substrate by dip-coating technique is reported. Critical current density measurements were done over an applied magnetic field using standard four probe technique and the results are compared with that of pure YBCO. High critical current density (J(c)) of similar to 4.84 MA/cm(2) at 77 K in self-field was obtained for 2 wt% of YBa2HfO5.5 added YBCO. A systematic increase ink observed in YBCO films prepared by the addition of nano HfO2, BaHfO3 and YBa2HfO5.5, attributed to the formation of a non-reacting 'derived secondary phase' YBa2HfO5.5 (YBHO) in the YBCO matrix. YBCO-YBa2HfO5.5 composite thick films have showed eightfold increases in J(c) (3.29 MA/cm(2)) at 77 K and 0.4 T compared to pure YBa2Cu3O7-delta film (0.37 MA/cm(2)), while maintaining a high transition temperature (T-c). The development of effective pinning centers in nano particle added YBCO thick film have enhanced the flux pinning force from 1.8 GN/m(3) for pure YBCO to a maximum value of 13.15 GN/m(3) for YBCO-YBa2HfO5.5. X-ray diffraction and energy dispersive spectroscopic analysis confirmed the presence of secondary phase, derived in the matrix. (C) 2015 Elsevier Ltd. All rights reserved.