Abstract
We developed a solution-derived method to establish a YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x quasi-trilayer architecture. Using the method, nano-scale pinning sites were induced into the quasi-trilayer architecture and yielded an apparent improvement in the in-field critical current density (Jc) of high-quality YBa2Cu3O7−x (YBCO). The improvement in the in-field Jc of the films was closely related to the thickness of the LaAlO3 (LAO) interlayer. In this paper it is demonstrated that when the nominal interlayer thickness approximates 20 nm, which is slightly higher than the roughness of the YBa2Cu3O7−x surface, the LaAlO3 interlayer is discontinuous due to synchromesh-like growth of the LaAlO3 layer on relatively rough YBa2Cu3O7−x surface resulting from the mobility of the solution. Nanoscale defects, such as particles, some amorphous phases, and especially their concomitant lattice defects (such as stacking faults and plane buckling) arise in YBa2Cu3O7−x layers. These nanoscale defects could play a role in flux pinning and thus enhancing Jc. The effective non-vacuum solution to induce vortex pinning into YBa2Cu3O7−x films could be a reference for the further design of an optimal pinning landscape for higher Jc.
Highlights
YBa2 Cu3 O7−x (YBCO)-coated conductors with high current-carrying capacity at liquid nitrogen temperature are currently thought to be the best candidates for power application1 [1,2,3,4,5]
The results demonstrated that an apparent improvement was achieved in the in-field Jc of high-quality YBCO by establishing a YBa2 Cu3 O7−x /LaAlO3 /YBa2 Cu3 O7−x quasi-trilayer architecture using the sol-gel method
The cause for the improved Jc was generally considered to be that the inserted layer suppressed Jc decay with increasing film thickness because the inserted layer could improve the epitaxial feature of the films; here, we show that the inserted layer could induce nanoscale defects into YBCO films, which behave as flux pinning sites
Summary
YBa2 Cu3 O7−x (YBCO)-coated conductors with high current-carrying capacity at liquid nitrogen temperature are currently thought to be the best candidates for power application1 [1,2,3,4,5]. It is well known, that the critical current density (Jc ) of YBCO-coated conductors or films decay exponentially with an applied magnetic field [6,7,8]. Enhancement of Jc in magnetic fields is urgently needed in order to produce higher-performance coated conductors or films. Foltyn’s group observed that anything that locally disrupts crystalline perfection on a scale of
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