Two level undercut-profile substrate for filamentary YBa₂Cu₃O₇coated conductors

Abstract

A novel substrate design is presented for scalable industrial production of filamentary coated conductors (CCs). The new substrate, called 'two level undercut-profile substrate (2LUPS)', has two levels of plateaus connected by walls with an undercut profile. The undercuts are made to produce a shading effect during subsequent deposition of layers, thereby creating gaps in the superconducting layer deposited on the curved walls between the two levels. It is demonstrated that such 2LUPS-based CCs can be produced in a large-scale production system using standard deposition processes, with no additional post-processing. Inspection of the conductor crosssection reveals that the deposited superconducting layer is physically separated at the 2LUPS undercuts. Filament decoupling is also seen in maps of the remanent magnetic field and confirmed by transport measurements.

Two Level Undercut-Profile Substrate-Based Filamentary Coated Conductors Produced Using Metal Organic Chemical Vapor Deposition

“…A gap is present in the GYBCO layer just below the edge of the upper plateau (marked by "A") that verifies the desired physical decoupling between the superconducting filaments. It was observed that the undercut length L = 1.2 ± 0.5 μm, which is significantly greater, compared to a previously reported Hastelloy-based 2LUPS sample (L=0.3 µm) [14]. In the curved region of the lower plateau (see Fig.2) the GYBCO layer is observed to be both porous and irregular, and as such considered non-functional.…”

“…Starting from a commercial Hastelloy C276 tape (L×W×T = 300 mm × 10 mm × 0.89 mm), wet electrochemical etching is employed in order to create the desired 2LUPS geometrical profile and to reduce the surface roughness [14].…”

“…The widths of each of the two lateral filaments are 2.8 ± 0.1 mm, while the five central plateaus has a width of 0.9 ± 0.1 mm. The reference sample was produced using the standard etching procedure [14]. Following the 2LUPS fabrication, the buffer and superconducting GYBCO layers are deposited on the substrate in a commercial production system at SuperPower Inc. by means of IBAD-MOCVD [15].…”

“…The challenge with these approaches comes from the reduction of the effective width of the superconducting (SC) layer that decreases the engineering critical current density, in addition to potential critical damage over the long length. Filamentization can potentially be achieved without reduction of the effective width of the tape using the two level undercut profile substrate (2LUPS) concept [13], [14] (see Fig. 1), consisting of two levels of plateaus in the metal substrate surface separated by a vertical displacement with an undercut profile.…”

Spark-Discharge Plasma as a Method to Produce Low AC Loss Multifilamentary (RE)Ba2Cu3 O7 Coated Conductors

“…Previous methods including mechanical scribing [6], [7], laser striation [8]- [10], inkjet printing [11]- [13] and substrate templating [14], [15] have been used to divide CC's into filaments. In the current work an alternative method using high temperature plasma, which occurs during an electrical sparkdischarge between electrode and tape surface, is presented.…”