Sm-Co Permanent Magnet Microstructure for High-Temperature Coercivity
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Solution Overview
Problem
Permanent magnets in rotating electric machines face challenges in achieving both high magnetic flux density and coercive force while maintaining heat resistance and preventing thermal demagnetization, especially at elevated temperatures.
Innovation Solution
A permanent magnet with a specific composition and structure, including a Th2Zn17 crystal phase, a cell wall phase, and a platelet phase intersecting with the Th2Zn17 crystal phase, where the average distance between platelet phases is between 10 nm and 30 nm, and the composition is represented by R p Fe q M r Cu t Co 100-p-q-r-t, with R being rare earth elements, M being Zr, Ti, or Hf, and optimized concentrations of Fe, Cu, and Co, enhancing coercive force and residual magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the Fe concentration is increased to increase magnetic flux density, then the magnetic flux density is improved, but the coercive force becomes small and thermal demagnetization is easily to occur
Solution Approach 1:
The patent applies local quality by creating a non-uniform Cu concentration distribution within the permanent magnet structure. Specifically, Cu is concentrated in the cell wall phase (forming a Cu-rich phase) while the cell phase maintains lower Cu concentration. This local differentiation allows the Cu-rich cell wall phase to provide pinning sites for domain walls, enhancing coercive force, while the cell phase maintains adequate magnetization. This resolves the contradiction by locally optimizing different regions for different functions: the cell wall phase for coercivity and the cell phase for magnetic flux density.
Solution Approach 2:
The patent employs composite materials by creating a multi-phase structure consisting of a cell phase (Th2Zn17-type) and a Cu-rich phase (1-5-type or similar) distributed in the cell walls. This composite structure combines the advantages of different phases: the Th2Zn17 phase provides high magnetization and the Cu-rich phase provides enhanced coercive force through domain wall pinning. The composite nature allows simultaneous achievement of high magnetic flux density and high coercive force, resolving the technical contradiction between these two parameters.
2Weight of moving object
If the motor size and weight are reduced while maintaining high output, then the size and weight are improved, but the heat generation density is increased and temperature of the motor is easily increased
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition parameters of the permanent magnet. Specifically, it controls the Rare earth content (10-14.5 at%), Fe content (17-26 at%), Cu content (0.5-9.0 at%), and introduces M elements (Zr, Ti, or Hf) at controlled amounts (1.5-4.2 at%). These parameter optimizations enable the magnet to maintain high coercive force and resist thermal demagnetization even at elevated temperatures, allowing motor downsizing without compromising thermal performance.
Solution Approach 2:
The patent converts the harmful effect of high temperature (which normally causes thermal demagnetization) into a benefit by developing a permanent magnet with enhanced high-temperature stability. Through the specific composition design and multi-phase structure, the magnet achieves high coercive force that is maintained even at elevated temperatures. The Cu-rich phase creates energy barriers that prevent thermal activation of domain wall motion, effectively converting the thermal energy that would cause demagnetization into a condition that maintains magnetic stability.
3Reliability
If a Sm-Co-based magnet is used to achieve high heat resistance, then the heat resistance is improved, but the magnetic flux density is limited and coercive force becomes small at high Fe concentration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters: Rare earth content (10-14.5 at%), Fe content (17-26 at%), Cu content (0.5-9.0 at%), and M element content (1.5-4.2 at%). This optimized parameter range achieves a balance between heat resistance and magnetic flux density, overcoming the limitation of conventional Sm-Co magnets where high Fe concentration reduces coercive force. The specific parameter optimization enables simultaneous achievement of high magnetic flux density and high temperature stability.
Solution Approach 2:
The patent uses composite materials by creating a multi-phase structure with a cell phase (Th2Zn17-type) and a Cu-rich phase (1-5-type or similar). This composite structure allows the cell phase to provide high magnetization (contributing to magnetic flux density) while the Cu-rich phase provides enhanced coercive force through domain wall pinning at the phase boundaries. The composite nature resolves the contradiction between magnetic flux density and coercive force in Sm-Co-based magnets.
Data Source
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AI summary
According to an embodiment, a permanent magnet has a composition represented by a composition formula: RpFeqMrCutCo100-p-q-r-t (where, R is at least one element selected from rare earth elements, M is at least one element selected from Zr, Ti, and Hf, p is a number that satisfies 10.0 at% ≤ p ≤ 14.5 at%, r is a number that satisfies 1.5 at% < r ≤ 4.2 at%, t is a number that satisfies 0.5 at% ≤ t ≤ 9.0 at%, and q is a number that satisfies 17.0 at% ≤ q ≤ 26.0 at%); and a metallic structure including a cell phase having a Th2Zn17 type crystal phase, a cell wall phase formed so as to partition the Th2Zn17 type crystal phase, and a platelet phase formed so as to intersect with a c-axis of the Th2Zn17 type crystal phase, in which an average distance between the platelet phases is 10 nm or more and 30 nm or less.