Synthesis, structure and superconducting properties of laminated thin film composites of YBа2 Cu3 O7–d /Y2 O3 as components of 2G HTS wires

Abstract

2G HTS wires are capable of transferring huge amounts of electrical energy without loss. An increase in the current-carrying capacity in these materials is possible due to an increase in the thickness of the superconducting layer; however, there is a problem with the appearance of impurity orientations and other defects with increasing thickness. We have proposed a solution of this problem by increasing the thickness of the superconducting layer by the MOCVD method using interlayers of yttrium oxide. The aim of this study was the production of thick composite films with yttrium oxide interlayers and high critical current density. In addition, we want to show the effectiveness of the approach of introducing yttrium oxide interlayers for the reduction of the number of parasitic orientations and defects with an increase in HTS film thickness. The deposition of YBа2Cu3O7–dand Y2O3 films was carried out layer by layer using reel-to-reel MOCVD equipment. A 12 mm wire of the following architecture was used as a substrate: 200 nm CeO2 (Gd2O3)/30–50 nm LaMnO3/5–7 nm IBAD-MgO/50 nm LaMnO3/50 nm Al2O3/60 μ Hastelloy 276. The resulting films were annealed in oxygen for obtaining the orthorhombic YBCO phase. YBа2Cu3O7–d /Y2O3composites were obtained. In these composites, obtained using the MOCVD method, the amount of side (с║) orientation of the HTS layer was reduced and high values of the critical current density, exceeding 1 MA/cm at a thickness of > 2 μm remained. The efficiency of the approach of introducing yttrium oxide interlayers for the increase in the current characteristics with increasing film thickness was shown. It was found that further thickening of films with interlayers is prevented by the formation of nanopores, reducing the critical current density.

Keywords

• ybco
• mocvd
• heterostructures
• buffer layers
• y2o3
• hts
• superconductor