Rare Earth Magnet High-Temperature Coercive Force
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Solution Overview
Problem
R-Fe-B-based rare earth magnets experience a reduction in coercive force when exposed to high temperatures, which is a challenge for their application in high-power motors where self-heating occurs.
Innovation Solution
A rare earth magnet composition represented by Nd x (Ce, La) (1-x-y) R 1< y) p Fe (100-p-q-r-s) Co q B r M 1< s · (R 2< z R 3< w M 2< 1-z-w ) t, where R 1< and R 2< are rare earth elements, and an intermediate phase is introduced between the main and grain boundary phases, with specific content ratios and heat treatment processes to maintain coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an R-Fe-B-based rare earth magnet is used to maintain high performance, then strong magnetism is achieved, but the coercive force decreases at high temperatures
Solution Approach 1:
The patent applies local quality by creating distinct regions with different compositions: the main phase (R2Fe14B) provides strong magnetism, while the grain boundary phase (rich in R and B) provides magnetic isolation. This spatial differentiation of composition and function allows the magnet to maintain high coercive force at elevated temperatures through effective grain boundary isolation that prevents magnetic domain wall propagation.
Solution Approach 2:
The patent employs composite materials by combining multiple phases with complementary functions: the R2Fe14B main phase delivers high saturation magnetization, while the grain boundary phase (containing excess R and B elements) provides magnetic isolation. This multi-phase composite structure enables the magnet to simultaneously achieve strong magnetism and high-temperature stability.
2Strength
If the grain boundary phase is used to magnetically isolate main phases, then coercive force is enhanced, but magnetic performance is reduced due to excessive isolation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition and thickness of the grain boundary phase. By adjusting the R and B content in the grain boundary phase and optimizing its thickness (5-50 nm), the patent achieves optimal magnetic isolation that enhances coercive force while maintaining sufficient magnetic coupling for high overall magnetic performance.
Data Source
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AI summary
[SUMMARY] [PROBLEM TO BE SOLVED] To provide a rare earth magnet protected from reduction in the coercive force at high temperatures and a production method thereof. [MEANS TO SOLVE THE PROBLEM] A rare earth magnet comprising a main phase and a grain boundary phase present around the main phase, wherein: the overall composition is represented by the formula: (Ndx(Ce, La)(1-x-y)R1y)pFe(100-p-q-r-s)CoqBrM1s·(R2zR3wM21-z-w)t, wherein R1 is one or more members selected from rare earth elements other than Nd, Ce and La, R2 is one or more members selected from Pr, Nd, Pm, Sm, Eu and Gd, R3 is one or more members selected from rare earth elements other than R2, M1 and M2 are a predetermined element, 5.0≤p≤20.0, 0≤q≤8.0, 4.0≤r≤6.5, 0≤s≤2.0, 0≤t≤10.0, 0.4≤x≤0.8, 0≤y≤0.1, 0.5≤z≤0.8, and 0≤w≤0.1 and La is contained in an amount of 1/9 to 3 times by molar ratio relative to Ce.