Flux-pinning properties of YBa2Cu3O7−x multilayered films with Y2O3 and ZnO nanoparticle inclusions

Abstract: We investigated the flux-pinning properties of YBa₂Cu₃O_7−x (YBCO) films in which Y₂O₃ and ZnO nanoparticles were uniformly embedded by using the pulsed laser deposition (PLD) technique. Y₂O₃ and ZnO nanoparticles with average sizes of 10–30 nm and with different densities by changing the number of nanoparticle layers were introduced in a YBCO matrix in the form of a multilayered structure. The total thickness of the YBCO superconducting layers was kept to be 250 nm. Dilute doping was found to be effective for both Y₂O₃ and ZnO nanoparticles. For Y₂O₃ doping, critical current density (J _c ) enhancements over a wide range of fields were obtained in 1- and 5-layer doped samples, while weak J _c enhancements and a better field dependence of J _c were found in the YBCO film with 1 layer of ZnO. Based on an analysis of surface morphology, the transition temperature (T _c ), and J _c , we discuss the difference between the two types of nanoparticles as flux-pinning centers.