La(Fe,Si)13-Based Alloy Composition for Stable Magnetic Refrigeration
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Solution Overview
Problem
Magnetic materials used in magnetic refrigeration face instability and phase separation due to hydrogen insertion, leading to uneven Curie temperatures and reduced entropy change, while replacing iron with cobalt decreases magnetization and entropy change.
Innovation Solution
A unit comprising two alloys with different compositions, where the lanthanum element in La(Fe,Si)13-based alloys is replaced with group 1 or 2 elements, allowing for controlled Curie temperature and entropy change, and phase transition temperatures, enabling efficient temperature control through magnetic entropy changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hydrogen atoms are inserted into the interstitial sites of the crystal to increase the Curie temperature, then the Curie temperature is increased, but the crystal composition ratio becomes uneven and separation into two phases occurs
Solution Approach 1:
The patent changes the chemical composition parameters by replacing lanthanum elements with group 1 or 2 elements (such as Ce, Pr, Nd, Sr, Ba) to adjust the Curie temperature. This substitution method achieves Curie temperature control without causing the phase separation issues that occur with hydrogen insertion, as evidenced by the stable single-phase structure maintained in the modified alloys.
Solution Approach 2:
The patent introduces group 1 or 2 elements as intermediary substances to replace lanthanum in the La(Fe,Si)13-based alloy structure. These intermediary elements serve as substitutes that can adjust the Curie temperature through their different atomic sizes and electronic configurations without causing the hydrogen atoms to migrate and create composition inhomogeneity.
2Temperature
If iron atoms are replaced with cobalt atoms to change the Curie temperature, then the Curie temperature is adjusted, but the magnetization and entropy change decrease
Solution Approach 1:
The patent changes the lanthanum site occupancy with group 1 or 2 elements rather than replacing iron with cobalt. This alternative parameter change approach adjusts the Curie temperature through lattice parameter modification and electronic structure changes at the lanthanum site, preserving the iron-based magnetic substructure and maintaining high magnetization and entropy change values.
Solution Approach 2:
The patent applies local quality modification by specifically targeting the lanthanum sites for substitution with group 1 or 2 elements, while leaving the iron and silicon sites intact. This localized modification at the non-magnetic lanthanum positions allows Curie temperature adjustment without degrading the magnetic properties that depend on the iron sublattice.
3Temperature
If a single alloy composition is used to control Curie temperature, then the Curie temperature is set, but temperature control efficiency is reduced
Solution Approach 1:
The patent segments the temperature control function by creating multiple alloy types with different group 1 or 2 element substitutions, each having distinct Curie temperatures. This segmentation allows the system to address different temperature control requirements with specialized alloy compositions, improving overall temperature control efficiency through optimized matching between alloy properties and application needs.
Solution Approach 2:
The patent employs composite material strategies by combining La(Fe,Si)13-based alloys with different group 1 or 2 element substitutions to create a family of composite alloy systems. Each composite alloy in the family has tailored properties for specific temperature ranges, enabling efficient temperature control across broader applications through selective use of appropriate composite compositions.
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 solution stabilizes the crystal structure, maintains entropy change, and allows for precise temperature control, addressing the instability and phase separation issues in magnetic refrigeration.
Implementation Method 1
causing a magnetic entropy change
Data Source
AI summary
A unit includes a first alloy and a second alloy. The first alloy has a structure in which, in a crystal structure of a La(Fe,Si)13-based alloy, a lanthanum element position is replaced with a group 1 element other than hydrogen or a group 2 element. The second alloy has a structure in which, in a crystal structure of a La(Fe,Si)13-based alloy, a lanthanum element position is replaced with a group 1 element other than hydrogen or a group 2 element and has a composition different from that of the first alloy.