Flux pinning characteristics of Sn-doped YBCO film by the MOD process

Abstract

Compared with the undoped YBa2Cu3O7−δ (YBCO) film, 10mol% Sn-doped YBCO film exhibited significantly enhanced critical current densities (Jc) in magnetic fields up to 5T at 65 and 77K for H//c, indicating that the Sn-doped YBCO film possesses more effective flux pinning centers. Both samples were grown on the SrTiO3 (STO) (100) single crystal substrates by the metal-organic deposition (MOD) process. Larger Jc (77K, 1T) values of Sn-doped YBCO film are observed over a wide field-orientation angle (θ) except the field-orientations close to the ab-plane of YBCO (85°<θ<95°). Smaller Jc values for 85°<θ<95° in Sn-doped YBCO film are most probably caused by a reduced intrinsic pinning effect along the ab-plane due to high density Sn-containing nanoparticles trapped in the YBCO matrix. The effective pinning centers in Sn-doped YBCO film are attributable to Sn-containing nanoparticles trapped in the YBCO matrix which could be identified as the YBa2SnO5.5 (YBSO) phase by STEM (scanning transmission electron microscopy)-EDS (energy dispersive X-ray spectroscopy) analysis. Further analyses by HR-TEM (high resolution-transmission electron microscopy) revealed that YBSO nanoparticles completely surrounded by the YBCO matrix had random orientation with YBCO while those located at the interface of YBCO/STO substrate had epitaxial relationship with YBCO.