Structural identification of Ti compounds as YBa 3 Ti 2 O 8.5 in YBa 2 Cu 3 O 7-δ thin films through trifluoroacetate metal-organic deposition

The high-temperature superconductor YBa 2 Cu 3 O 7-δ (YBCO) exhibits a high critical temperature and an excellent critical current density; however, the degradation of its critical current density under external magnetic fields remains a significant issue hindering its practical applications. Therefore, the introduction of artificial pinning centers on the superconductor has been extensively investigated. In YBCO thin films fabricated using the metal-organic deposition (MOD), artificial pinning materials such as BaZrO 3 and BaHfO 3 precipitate within the films when the corresponding metal salts are added to the precursor solutions, and their compositions and crystal structures of these precipitates have been systematically studied and optimized. By contrast, Ticontaining compounds formed by the addition of Ti salts have generally been reported as BaTiO 3 ; however, their exact composition and crystal structure have not been clarified. In this study, YBCO thin films with added Ti salt were fabricated using MOD.The Ti-containing compounds precipitated within the films were identified through detailed analyses of the microstructure and elemental distribution. Crystallographic analysis combining fast Fourier transform patterns obtained from scanning transmission electron microscopy images and X-ray diffraction θ-2θ scans revealed that, under the conditions of this study, the Ti-containing compound was YBa 3 Ti 2 O 8.5 , with a hexagonal crystal structure. These results demonstrate that YBa 3 Ti 2 O 8.5 can be used as an artificial pinning center that can be controlled by optimizing the solution composition and heat-treatment conditions. Thus, this study provides guidance for the further enhancement of the current transport properties of YBCO-coated conductors.