Ce-Containing R-T-B Permanent Magnet Grain Boundary for High Coercivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rare earth magnets with high coercivity (HcJ) are costly due to the use of expensive rare earth elements, and there is a need for a magnet with improved magnetic properties using cerium (Ce) that balances cost and performance.
Innovation Solution
An R-T-B based permanent magnet with a composition including an R2T14B compound, a grain boundary with an R-rich phase and an R-T phase, and a specific area ratio of the R-T phase to the grain boundary, where Ce constitutes 15-35 mass % of the rare earth elements, enhancing coercivity without increasing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive rare earth elements are used to achieve high coercivity, then magnetic properties are improved, but material cost increases
Solution Approach 1:
The patent replaces expensive rare earth elements (such as Nd, Pr, Dy) with cheaper cerium (Ce) in the R2T14B compound, while compensating for the lower intrinsic coercivity of Ce through optimized grain boundary design. This substitution directly addresses the cost issue while maintaining magnetic performance through structural compensation.
Solution Approach 2:
The patent creates a composite grain boundary structure containing both R-rich phase and R-T phase, where the R-T phase (with area ratio 0.60-0.85) provides enhanced coercivity. This composite approach allows the use of cheaper Ce in the main phase while the specialized grain boundary phases compensate for performance losses, achieving both cost reduction and high coercivity.
2Quantity of substance
If Ce content is increased to reduce cost, then material cost decreases, but coercivity may be insufficient
Solution Approach 1:
The patent optimizes the Ce content parameter within a specific range (15-35 mass%) rather than using maximum Ce content. This controlled parameter change ensures cost reduction while preventing excessive Ce from compromising coercivity. The specific range is determined to balance cost and magnetic performance.
Solution Approach 2:
The grain boundary phases act as intermediaries that mediate between the Ce-containing main phase and the magnetic performance requirement. The R-T phase in the grain boundary (with area ratio 0.60-0.85) serves as a mediator to enhance coercivity, allowing the use of cost-effective Ce in the main phase while achieving sufficient overall coercivity through the grain boundary's mediating effect.
3Reliability
If grain boundary composition is optimized for high coercivity, then magnetic properties are improved, but production complexity increases
Solution Approach 1:
The patent specifies a quantitative range for the R-T phase area ratio (0.60-0.85) in the grain boundary, providing a clear production target. This parameter-based approach simplifies production control compared to qualitative descriptions, as manufacturers can directly control and measure the area ratio to ensure consistent high coercivity performance.
Data Source
AI summary
An R-T-B permanent magnet that contains: main-phase grains composed of an R2T14B compound (where R is a rare earth element, T is a transition metal element, and B is boron); and grain boundaries. R includes Ce. The R-T-B permanent magnet has a Ce content of 15-35 mass % with respect to the total R content. The grain boundaries include an R-rich phase and an R-T phase. In a cross section of the R-T-B permanent magnet, the surface area ratio S(R-T) of the R-T phases with respect to the grain boundaries is 0.60-0.85.