Sm-Co-Fe-Cu Permanent Magnet Composition for High Coercivity
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Solution Overview
Problem
Existing permanent magnets, such as Sm-Co-based magnets, face challenges in achieving high residual magnetization, squareness ratio, and coercive force while maintaining sufficient heat resistance and sintered body density, especially at high Fe concentrations.
Innovation Solution
A permanent magnet with a composition formula R_pFe_qM_rCu_tCo_100-p-q-r-t, where R is a rare-earth element, M is Zr, Ti, or Hf, and specific atomic percentages are used to create a sintered body with Th2Zn17 crystal phases and controlled oxide phases at grain boundaries, optimizing coercive force and squareness ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If part of Co is replaced by Fe and Fe concentration is increased to increase magnetization, then residual magnetization is improved, but sintered body density and squareness ratio deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Fe concentration within 25-35 atomic percent and Cu concentration within 5-15 atomic percent. This optimization of compositional parameters enables the magnet to achieve high residual magnetization while maintaining sufficient sintered body density and squareness ratio, resolving the contradiction between increasing magnetization and maintaining manufacturing precision
Solution Approach 2:
The patent creates a composite material system by combining Sm-Co-Fe-Cu elements with specific atomic percentages. The composite structure with controlled multi-element composition allows the magnet to simultaneously achieve high residual magnetization through Fe addition while maintaining structural integrity and magnetic properties through Cu addition and precise compositional control
2Temperature
If Dy is used to replace part of Nd to increase heat resistance, then heat resistance is improved, but material availability and cost worsen due to Dy being a rare-earth element
Solution Approach 1:
The patent replaces expensive and scarce Dy with a more abundant and cost-effective Sm-Co-Fe-Cu composition system. By using readily available elements in optimized proportions, the invention achieves comparable or superior heat resistance without relying on critical rare-earth elements like Dy, thereby improving material availability and reducing cost
Solution Approach 2:
The patent changes the compositional parameters from a Nd-Dy-based system to a Sm-Co-Fe-Cu-based system with specific atomic percentages. This parameter change enables the magnet to achieve high heat resistance through controlled composition rather than relying on Dy addition, resolving the contradiction between heat resistance and rare-earth element availability
3Temperature
If Sm-Co-based magnet is used instead of Nd-Fe-B-based magnet to avoid Dy, then heat resistance is improved, but maximum energy product (BH)max deteriorates
Solution Approach 1:
The patent creates an optimized composite material by combining Sm, Co, Fe, and Cu elements in specific atomic percentages. This composite structure leverages the heat resistance of Sm-Co while incorporating Fe to enhance magnetization and Cu to improve coercive force, thereby achieving high maximum energy product that overcomes the traditional limitation of Sm-Co-based magnets
Solution Approach 2:
The patent fundamentally changes the compositional parameters of Sm-Co-based magnets by adding Fe (25-35 atomic percent) and Cu (5-15 atomic percent) in optimized ratios. These parameter changes transform the material properties to achieve both high heat resistance and high maximum energy product, resolving the contradiction between heat resistance and power output
Data Source
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AI summary
A high-performance permanent magnet is provided. The magnet is expressed by a composition formula: RpFeqMrCutCo100-p-q-r-t. The magnet includes a sintered body including: a plurality of crystal grains each having a Th2Zn17 crystal phase; and a plurality of grain boundaries between the crystal grains. If an oxide phase of the R element is defined by a continuous region that is disposed in the sintered body and contains the R element and oxygen having a concentration of 85 atomic percent or more, a ratio of the number of the oxide phases in the grain boundaries to the number of the crystal grains is 1.1 or less.