Polycrystalline Superconductor Composition for Stable Tc and Jc
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Solution Overview
Problem
The production of BaK122 polycrystalline bulk bodies is hindered by the high vapor pressures of Ba and K, leading to varying substitution content x, which affects the superconducting properties (Tc and Jc) each time the compound is produced.
Innovation Solution
A polycrystalline bulk body composed of iron-based compound AA′Fe4As4 with a fixed 1:1 compositional ratio of A and A′, where A is Ca and A′ is K, and a production method involving mixing, pressurizing, and heating steps to stabilize superconducting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ba and K are used in the chemical formula (Ba1-xKx)Fe2As2, then superconductivity is achieved with varying Tc and Jc, but the high vapor pressures of Ba and K cause them to evaporate easily and in different degrees during production, leading to varying substitution content x and unstable superconducting properties
Solution Approach 1:
The patent changes the chemical composition parameters by replacing Ba with Ca and part of A with Sr or Eu, and replacing K with elements from Group 1 (K, Rb, Cs). This substitution fundamentally alters the vapor pressure characteristics of the compound, eliminating the evaporation problem while maintaining the superconducting properties. The new composition AA′Fe4As4 with A:A′ ratio of 1:1 fixes the substitution content, ensuring stable Tc and Jc values across different production batches.
2Manufacturing precision
If the substitution content x is varied to optimize Tc and Jc, then superconducting properties can be tuned, but the high vapor pressures cause the substitution content to vary each time of production, making it difficult to achieve consistent results
Solution Approach 1:
The patent fixes the compositional ratio parameter by defining the chemical formula as AA′Fe4As4 where A and A′ are in a 1:1 ratio. This fixed stoichiometry eliminates the variability of substitution content x that plagues the (Ba1-xKx)Fe2As2 system. By changing to this new compositional framework with lower vapor pressure elements, the invention achieves both manufacturing precision and repeatability of superconducting properties.
3Temperature
If BaK122 is used as the base compound, then superconductivity is achieved, but the production cost increases and the operating temperature range is limited compared to the new AA′Fe4As4 compound
Solution Approach 1:
The patent changes the base compound parameters from BaK122 to AA′Fe4As4, where A is Ca with optional substitution by Sr or Eu, and A′ is selected from K, Rb, or Cs. This compositional change enables operation at higher temperature ranges while using more abundant and cost-effective elements. The new compound structure with fixed 1:1 ratio simplifies production control and reduces costs compared to the variable composition BaK122 system.
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
The method ensures uniform superconducting properties and reduces production costs by fixing the compositional ratio, allowing for higher Tc and Jc stability and repeatability.
Implementation Method 1
the iron-based compound exhibiting superconductivity in a temperature range below a critical temperature
Implementation Method 2
a pressurizing step of pressurizing a mixture resulting from the mixing in the mixing step
Implementation Method 3
a heating step of heating the mixture at a temperature of not less than 750° C. and not more than 1000° C. in a state where the mixture is sealed in a container
Data Source
AI summary
A polycrystalline bulk body of this invention has uniformity in superconducting properties, in comparison to a polycrystalline bulk body including crystal grains each constituted by (Ba1-xKx)Fe2As2. A polycrystalline bulk body (1) of this invention includes crystal grains each constituted by an iron-based compound (10) expressed by chemical formula AA′Fe4As4, where A is Ca and A′ is K, the iron-based compound (10) having a crystal structure in which AFe2As2 layers (16) and A′Fe2As2 layers (17) are alternately stacked.