Microstructure of YBa2Cu3Oy coated conductor using {100} ⟨001⟩ textured Cu tape with dual functions of metal substrate and electric stabilizing layer in order to develop low-cost high-TC superconducting wires

Ataru Ichinose,Toshiya Doi,Iwao Kawayama,Tsuyoshi Hamada,Keisuke Ota

doi:10.1063/5.0021082

Abstract

A new configuration of coated conductors (CCs), REBa2Cu3Oy (RE: rare earth elements such as Sm, Eu, Gd, and Y)/(Sr, La)TiO3 conductive buffer/Ni-electroplated {100}⟨001⟩ textured Cu and SUS316 lamination tape, has been proposed to reduce material costs. This conductive buffer layer is slightly modified from the previously reported Sr (Ti, Nb)O3 conductive buffer layers by changing the substitution element and site. However, a drastic change is found in the electric resistivity of the conductive buffer layers after oxygen annealing of YBa2Cu3Oy. The resistivity of Sr(Ti, Nb)O3 conductive buffer layers increases by more than three orders of magnitude, while the resistivity of (Sr, La)TiO3 is almost maintained and only minimally increases. Microscopic structural analysis of the CCs using the newly proposed conductive buffer layer is conducted using transmission electron microscopy (TEM). A very clean interface between the metal tape and the conductive buffer layer in the 600 nm thick (Sr, La)TiO3 buffer layers is confirmed by the TEM analysis, which has no reactive layers as well as no inter-diffusion of oxygen and metal elements. This result will soon lead to the development of low-cost and high-performance CCs.

Highlights

One or two km length REBa2Cu3Oy (REBCO) (RE: rare earth elements such as Sm, Eu, Gd, and Y) coated conductors (CCs) have been commercialized worldwide to develop superconducting electric power equipment.1–7 to increase the REBCO CC’s market globally, the material and manufacturing costs must be reduced to decrease the price
Several similar attempts using conductive buffers combined with a cube-textured Cu tape have been previously reported,12–15 to our knowledge, no one has succeeded in fabricating a coated conductor using a Cu metal tape substrate that functions as a stabilizing layer and a REBCO biaxially oriented template
According to a two-dimensional current flow simulation of the REBCO CC in the YBCO quenching caused by a microcrack, the current transferring length required for current transfer to Cu was estimated to be about 1 mm when the electric resistivity was 1 × 10−3 Ω ⋅ cm,16 and it was found that heat generated by the current in each segment could be removed by liquid nitrogen

Summary

Introduction

One or two km length REBa2Cu3Oy (REBCO) (RE: rare earth elements such as Sm, Eu, Gd, and Y) coated conductors (CCs) have been commercialized worldwide to develop superconducting electric power equipment. to increase the REBCO CC’s market globally, the material and manufacturing costs must be reduced to decrease the price. A configuration for REBCO CCs in combination with conductive buffer layers and a high-conductivity metal tape has been proposed to reduce the material costs.. This proposal concept is that the function of electric stabilizing layers fabricated directly on a superconducting layer is transferred to a thick metal substrate. This eliminates the most expensive silver required to deposit copper on a superconducting layer. Mainly conductive buffer layers should be developed for low-cost CCs. several similar attempts using conductive buffers combined with a cube-textured Cu tape have been previously reported, to our knowledge, no one has succeeded in fabricating a coated conductor using a Cu metal tape substrate that functions as a stabilizing layer and a REBCO biaxially oriented template. We believe the challenging attempt is to find a suitable conductive oxide buffer layer

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Conclusion