Abstract
Chemical solution deposition of Gd-doped YBCO, Y1GdyBa2Cu3O7−δ, (YBCO-Gd), film was carried out following the metal-organic decomposition approach and in situ route. Two dopant concentrations, 5 and 10 mol %, were evaluated. The morphology and crystalline structure of the superconductor films were deeply investigated. In general, a homogeneous and well c-axis oriented film was observed by using scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction. However, compared to pure YBCO, YBCO-Gd samples showed an increased stacking faults concentration, as recognized by TEM. X-ray photoelectron spectroscopy allowed studying the Gd distribution in the films and gathered information about the Gd electronic environment. Superconducting properties were evaluated at different temperatures, magnetic field directions, and intensities. Higher zero-field critical current densities were measured with respect to undoped samples in the temperature range from 10 to 77 K with both Gd concentrations (i.e., 28, 27, and 13 MA·cm−2, respectively, for YBCO-Gd 5%, YBCO-Gd 10%, and undoped YBCO at 10 K in self field condition). At low temperatures, this improvement was maintained up to 12 T, confirming the efficacy of Gd addition for the enhancement of transport properties of YBCO film.
Highlights
Several studies have been carried out on the substitution of Y3+ in YBa2 Cu3 O7−δ (YBCO) by rare earth elements (RE), such as Er3+, Ho3+, and Gd3+, to form REBa2 Cu3 O7−δ (REBCO) compounds
From a detailed analysis of the 001 reflections, it can be observed that all samples with Gd doping were characterized by the presence of a broad peak at a lower angle with respect to the YBCO
This feature might be ascribed to the presence of Y2 Ba4 Cu7 O15 (Y247) phases or Y1 Ba2 Cu4 O8 (Y124) (e.g., PCPDF card # 473–410), suggesting, a higher amount of stacking faults in these samples
Summary
Several studies have been carried out on the substitution of Y3+ in YBa2 Cu3 O7−δ (YBCO) by rare earth elements (RE), such as Er3+ , Ho3+ , and Gd3+ , to form REBa2 Cu3 O7−δ (REBCO) compounds. Their superconducting properties are generally improved with respect to YBCO due to the higher critical temperature (Tc ) values and, higher irreversibility fields (Hirr ) at 77 K [1]. With respect to pure YBCO, chemical solution deposition (CSD) of GdBCO film requires more accurate control of the process parameters, especially during the crystallization step. GdBCO nucleation is favored by higher growth temperatures, faster ramp rates, and lower oxygen partial pressure (pO2 ) than those used in the YBCO process [8,9,10,11]
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