Core-Shell Rare Earth Magnet Composition With Reduced Heavy Rare Earth Use
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Solution Overview
Problem
The high cost and scarcity of heavy rare earth elements pose a challenge in maintaining the coercive force of rare earth magnets, as they are expensive and their price is expected to rise further, necessitating a reduction in their usage while preserving the enhancement of coercive force.
Innovation Solution
A rare earth magnet with a core/shell structure is developed, where the molar ratio of heavy rare earth elements is higher in the shell part than in the core part, and a modifier containing both a heavy rare earth element and Ce is used to diffuse and penetrate into the magnet precursor, allowing Ce to occupy the 4f site and the heavy rare earth element to occupy the 4g site, enhancing the coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements are used to enhance coercive force, then the coercive force is improved, but the cost increases and the amount of expensive material required increases
Solution Approach 1:
The patent applies local quality by creating a core/shell structure where the shell part contains a higher concentration of heavy rare earth elements than the core part. This localized distribution concentrates the coercive force enhancement effect in the shell region while reducing the overall amount of expensive heavy rare earth elements needed compared to uniform distribution throughout the entire magnet.
Solution Approach 2:
The patent uses composite materials by combining heavy rare earth elements with light rare earth elements (such as Ce, Pr, Nd) in a specific core/shell configuration. This composite structure leverages the high coercive force contribution of heavy rare earth elements in the shell while using cheaper light rare earth elements in the core, thereby reducing overall material cost while maintaining performance.
2Strength
If heavy rare earth elements are used to enhance coercive force, then the coercive force is improved, but the cost increases
Solution Approach 1:
By concentrating heavy rare earth elements in the shell part rather than distributing them uniformly, the patent reduces the total quantity of expensive material required. This local quality approach maintains the necessary coercive force enhancement at the magnet's surface while minimizing overall material cost.
Solution Approach 2:
The patent employs parameter changes by controlling the diffusion process to achieve specific concentration gradients of heavy rare earth elements. By adjusting diffusion time, temperature, and composition, the patent optimizes the distribution parameters to achieve adequate coercive force with minimized heavy rare earth element content, thereby reducing cost.
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 approach results in a higher coercive force than predicted by the content ratio of heavy rare earth elements, allowing for a reduction in their usage while maintaining the magnetic properties, thereby reducing costs.
Implementation Method 1
allowing a modifier containing both a heavy rare earth element and Ce to diffuse and penetrate into a rare earth magnet precursor
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3
AI summary
A rare earth magnet in which the amount used of a heavy rare earth element is more reduced while maintaining enhancement of the coercive force, and a producing method thereof are provided. The rare earth magnet of the present disclosure has a main phase (10) and a grain boundary phase (20). The main phase (10) has a composition represented by, in molar ratio, R1 2T14B (R1 is a rare earth element, etc. and T is a predetermined transition element, etc.). The main phase (10) has a core part (12) and a shell part (14). Denoting the abundances of R2 and Ce (R2 is a predetermined heavy rare earth element) occupying 4f site of the shell part (14) as R2 4f and Ce4f, respectively, and denoting the abundances of R2 and Ce occupying 4g site of the shell part (14) as R2 4g and Ce4g, respectively, the rare earth magnet satisfies 0.44≤R2 4g/(R2 4f+R2 4g)≤0.70 and 0.04≤(Ce4f+Ce4g)/(R2 4f+R2 4g). The rare earth magnet-producing method of the present disclosure uses a modifier containing at least R2 and Ce.