Study on advanced Ce_0.9La_0.1O₂/Gd₂Zr₂O₇ buffer layers architecture towards all chemical solution processed coated conductors

Abstract

Chemical solution deposition is a versatile technique to deposit functional oxide films with low cost. In this study, this approach was employed to grow multi-layered, second-generation, high-temperature superconductors ("coated conductors") with high superconducting properties. The Ce 0.9 La 0.1 O 2 / Gd 2 Zr 2 O 7 buffer layer stack and the 200 nm thick YBa 2 Cu 3 O 7 (YBCO) superconducting layer were sequentially deposited on textured NiW substrates using metal-organic deposition routes. The surface texture of the Gd 2 Zr 2 O 7 barrier layer deteriorates when the film thickness increases to 80 nm, although the global texture retains a sharp biaxial orientation, as determined by conventional X-ray diffraction. We paid particular attention to improving the surface quality in terms of crystallographic orientation and local flatness after depositing a Ce 0.9 La 0.1 O 2 thin film as a cap layer. From a comprehensive analysis of the surface morphology and misorientation maps constructed by electron backscattering diffraction, it is found that these improvements are mainly attributed to: (i) the preferential nucleation of Ce 0.9 La 0.1 O 2 crystals on the Gd 2 Zr 2 O 7 grains with desirable orientations; and (ii) the predominant two-dimensional growth of the Ce 0.9 La 0.1 O 2 crystals in the layer. Moreover, the microstructure and superconducting performance of the YBCO superconducting layer were thoroughly characterized and compared with those of films deposited on single-crystal substrates using the same technique. A promising critical current density of 2.2 MA cm À2 (77 K, self-field) was achieved on such an all chemical derived configuration, demonstrating the high quality of the buffer layer stack and the feasibility of using all chemical solution routes for the fabrication of low-cost coated conductors.

Preparation of a Cube-Textured Ni-7at.%W Based Template Used for Coated Conductors

“…). The quality of present grown GZO film is almost identical to that in[17], where a high J c of 2.2 MAcm −2 in YBCO layer has been achieved employing GZO as buffer layer. Thus, it could be concluded that the high quality GZO film deposited on Ni7W substrates produced by once IAT rolling with optimum annealing parameters provides a promising GZO/Ni7W template for further deposition of buffer and superconducting layers.…”

“…Up to now, the textured Ni-7~9.5at.%W (Ni7~9.5W) alloy substrates have been developed using both powder metallurgy [4] [5] and melting routes [6]- [14]. Since the reduction of stacking fault energy in Ni-W alloy with high tungsten additions, several specific rolling techniques, in particular, the intermediate annealing [17]. In this case, the commercial Ni5W tapes were employed as textured substrates.…”

Strongly Enhanced Growth of High-Temperature Superconducting Films on an Advanced Metallic Template

“…Until now, mainly YBa 2 Cu 3 O 6+ x (YBCO) and GdBa 2 Cu 3 O 6+ x (GdBCO) has managed to grow on these buffered metallic templates utilizing PLD for the large-scale coated conductor manufacturing . However, these nonsingle crystalline templates are extremely harsh growth environments for the films to be deposited due to the presence of the great number of grain boundaries, which are usually transferred on the film deposited on the top of it. − This grain boundary transfer significantly diminishes the benefits of the HTS materials, such as liquid nitrogen cooling, as they limit the superconducting critial current more substantially in the high temperature range. The critical current, determined by the grain boundaries, has been observed to decrease linearly in zero field as the temperature is increased according to the superconductor–insulator–superconductor (SIS) model. − More unfortunately, under applied magnetic fields the critical current is suppressed exponentially as a function of temperature, and in some cases the grain boundaries can even become weak links blocking the applied current completely. , …”

A Two-Level Undercut-Profile Substrate for Chemical-Solution-Based Filamentary Coated Conductors

“…6 indicate that the texture in the GZO layer is characterized by a sharp {001}〈110〉 component, i.e. 45° rotated cube orientation [19]. There is almost no difference in the maximum intensity of this component between the lower and upper plateaus (cf.…”