Chemical Solution Deposition of Insulating Yttria Nanolayers as Current Flow Diverter in Superconducting GdBa₂Cu₃O_7−δ Coated Conductors

Abstract

The primary benefit of a metallic stabilization/shunt in high temperature superconductor (HTS) coated conductors (CCs) is to prevent joule heating damage by providing an alternative path for the current flow during the HTS normal state transition (i.e., quench). However, the shunt presence in combination with unavoidable fluctuations in the critical current ( I c ) of the HTS film can develop a localized quench along the CC’s length if the operational current is kept close to I c . This scenario, also known as the hot-spot regime, can lead to the rupture of the CC if the local quench does not propagate fast enough. The current flow diverter (CFD) is the CC architecture concept that has proven to increase the conductor’s robustness against a hot-spot regime by simply boosting the quench velocity in the CC, which avoids the shunt compromise in some applications. This work investigates a practical manufacturing route for incorporating the CFD architecture in a reel-to-reel system via the preparation of yttrium oxide (Y 2 O 3 ) as an insulating thin nanolayer (∼100 nm) on top of a GdBa 2 Cu 3 O 7 (GdBCO) superconductor. Chemical solution deposition (CSD) using ink jet printing (IJP) is shown to be a suitable manufacturing approach. Two sequences of the experimental steps have been investigated, where oxygenation of the GdBCO layer is performed after or before the solution deposition and the Y 2 O 3 nanolayer thermal treatment formation step. A correlated analysis of the microstructure, in situ oxygenation kinetics, and superconducting properties of the Ag/Y 2 O 3 /GdBCO trilayer processed under different conditions shows that a new customized functional CC can be prepared. The successful achievement of the CFD effect in the case of the preoxygenated customized CC was confirmed by measuring the current transfer length, thus demonstrating the effectiveness of the CSD-IJP as a processing method.

Enhanced Normal Zone Propagation Velocity in REBCO Coated Conductors Using an Intermetallic Stabilizer Coating

“…10 reveal a consistent 5-8x increase in the NZPV for both indium-altered samples. These values are very close to the ones measured during the FASTGRID project, where classical CFD samples were made with silver-coated tapes from THEVA [29] as well as coated conductors with an insulating Yttria layer with the CFD geometry [17], [29].…”

“…Results for the classic CFD, Yttria CFD and Pristine THEVA (i.e. no CFD) samples were taken from the FASTGRID project [17,29]. increase in the quench velocity, namely a 5-8x gain when compared to pristine silver-coated THEVA tapes.…”

“…One year later, another method using the Chemical Solution Deposition (CSD) of amorphous Yttrium Oxide (Y2O3) was successfully tested on THEVA GmbH CCs to form a CFD structure Ag/Y2O3/REBCO. However, the oxygenation of the REBCO film in the presence of the yttria-CFD layer could only be accomplished by inserting an intermediate extra step into the standard fabrication process [17], which would compromise the industry's throughput goals. Most recently, a novel approach was proposed based on a partial transformation of the Ag layer 2 IEEE-TAS -EUCAS23-4-MO-QC-02I into Ag2S to reach the so-called buffer-layer-CFD (bCFD) CC architecture, which also considerably enhances the NZPV [18].…”

Some Results of the EU Project FASTGRID

“…However, the CFD effect was poor due to electrical connections between the SC and metallization layers (numerous outgrowth peaks on the SC layer passing through the Yttria layer). Recently, new strategies with the Yttria route, especially improvements in the oxygenation process, showed very good results [19]. Other strategies have been investigated by ICMAB during FASTGRID.…”

A sulfurization method for creating the buffer-layers current flow diverter architecture in REBa2Cu3O7 coated conductors

“…More recently, another low-cost method using the chemical solution deposition of amorphous yttrium oxide (Y 2 O 3 ) was proposed to form a CFD trilayer Ag/Y 2 O 3 /REBCO on THEVA GmbH CCs. Although compatible with the REBCO layer, this yttria-CFD approach requires adding some extra steps to the traditional CC fabrication process [26].…”