Oxide Superconducting Wire Grain Orientation for Low Interlayer Resistance
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Solution Overview
Problem
Oxide superconducting wires experience increased connection resistance and joule heat at connection points due to soldering, and there is a challenge in bypassing current during quenching with reduced interlayer resistance between the superconducting and protective layers.
Innovation Solution
The superconducting layer is configured with a specific proportion of a-axis oriented grains, ranging from 4.1% to 11.9%, to reduce interlayer resistance, and in some cases, two superconducting layers with different a-axis oriented grain ratios are used to further enhance this effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If oxide superconducting wires are solder-connected to produce long wires, then wire length is increased, but connection resistance at the connection part increases and joule heat is generated
Solution Approach 1:
The patent changes the crystallographic orientation parameters of the superconducting layer by controlling the a-axis oriented grain ratio to be 10% or more, which fundamentally alters the electrical properties at the interface between the superconducting layer and protective layer, thereby reducing contact resistance and improving solder connection reliability
Solution Approach 2:
The patent creates a composite microstructure within the superconducting layer by combining c-axis oriented grains (for high critical current density) with a-axis oriented grains (for low contact resistance), achieving a balance between current carrying capacity and connection quality
2Length of moving object
If connection resistance increases, then wire length can be extended through soldering, but bypass current flow during quenching is reduced
Solution Approach 1:
By adjusting the a-axis oriented grain ratio to 10% or more, the patent modifies the interfacial resistance characteristics between the superconducting layer and protective layer, ensuring adequate bypass current pathways during quenching events while maintaining extended wire length capability
3Reliability
If the proportion of a-axis oriented grains is increased to reduce interlayer resistance, then contact resistance decreases, but critical current density may be affected
Solution Approach 1:
The patent optimizes the a-axis oriented grain ratio to be 10% or more but not exceeding a certain threshold, creating an optimal balance point where contact resistance is sufficiently reduced while critical current density remains above minimum required levels
Solution Approach 2:
The patent creates local regions with different grain orientations within the superconducting layer, where a-axis oriented grains are concentrated at the interface with the protective layer to reduce contact resistance, while c-axis oriented grains dominate the bulk to maintain high critical current density
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in reduced interlayer resistance and ensures a high critical current density in the longitudinal direction of the superconducting wire, allowing for the production of long wires with lower connection resistance.
Implementation Method 1
a-axis oriented grains having the a-axis oriented in a direction perpendicular to the main surface of the substrate have an effect on an interlayer resistance between the superconducting layer and the protective layer
Implementation Method 2
oxide superconducting wire having a reduced interlayer resistance
Data Source
Figure 1~2
Figure 3
AI summary
An oxide superconducting wire according to the invention includes a substrate having a main surface, a superconducting layer provided above the substrate and formed of a rare-earth high-temperature superconductor, and a protective layer provided on the superconducting layer and in contact with the superconducting layer. The superconducting layer includes a-axis oriented grains having an a-axis oriented in a direction perpendicular to the main surface of the substrate. An a-axis oriented grain ratio expressing a proportion of the a-axis oriented grains to an entirety of crystal grains forming the superconducting layer is in a range of 4.1 to 11.9%.