R-T-B Sintered Magnet Reverse Core-Shell Structure
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Solution Overview
Problem
Current R-T-B based sintered magnets face challenges in further improving coercive force and reducing costs while maintaining magnetic properties.
Innovation Solution
The development of an R-T-B based sintered magnet with a reverse core-shell main phase particle structure, where the core part has a higher concentration of heavy rare earth elements than the shell part, and a low RH crystal phase, along with a nonmagnetic R-rich phase, is introduced. This structure is achieved through a process involving decomposition, grain boundary diffusion, and rapid cooling, resulting in a lower crystal orientation degree in the magnet surface layer compared to the central part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth elements are added to improve coercive force, then coercive force increases, but production cost increases
Solution Approach 1:
The patent applies local quality by creating a reverse core-shell structure where heavy rare earth elements are concentrated in the core region rather than uniformly distributed. This localized concentration achieves high coercive force at the critical core regions while reducing overall usage. The shell region has lower heavy rare earth content, optimizing the balance between performance and cost.
Solution Approach 2:
The patent employs composite materials by combining phases with different heavy rare earth concentrations to form a reverse core-shell structure. This composite approach allows the material to exhibit enhanced coercive force through the heavy rare earth-rich core while the heavy rare earth-poor shell reduces overall material cost and maintains necessary magnetic properties.
2Force
If heavy rare earth elements are added to improve coercive force, then coercive force increases, but maximum energy product decreases
Solution Approach 1:
The reverse core-shell structure applies local quality by concentrating heavy rare earth elements in the core region to enhance coercive force locally, while the shell region maintains lower heavy rare earth content to preserve saturation magnetization. This spatial differentiation allows simultaneous optimization of both coercive force and maximum energy product.
Solution Approach 2:
The patent uses composite materials with a reverse core-shell structure where the core phase is rich in heavy rare earth elements for high coercivity, and the shell phase is poor in heavy rare earth elements for high saturation magnetization. This composite structure resolves the trade-off between coercive force and maximum energy product.
3Reliability
If crystal orientation degree is increased to improve magnetic properties, then magnetic properties improve, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating different crystal orientation characteristics in different regions: the core region has specific crystal orientation for high coercive force, while the shell region has different orientation characteristics. This regional differentiation achieves overall magnetic performance optimization without requiring uniform high-precision orientation control throughout the entire material.
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 enhances coercive force and residual magnetic flux density while reducing the usage of expensive heavy rare earth elements, thereby improving magnetic properties and lowering production costs.
Implementation Method 1
diffusing the heavy rare earth elements via grain boundaries by adhering the heavy rare earth elements on the surface and heating thereof
Implementation Method 2
decomposition, grain boundary diffusion, and rapid cooling, resulting in a lower crystal orientation degree
Data Source
AI summary
An R-T-B based sintered magnet including a main phase particle comprising an R2T14B type crystal structure. R is at least one rare earth element, T is at least one transition metal element essentially including Fe or Fe and Co, and B is boron. The R-T-B based sintered magnet includes a magnet surface layer part and a magnet central part existing inside the magnet surface layer part. A crystal orientation degree of the main phase particle in the magnet surface layer part having a magnetic pole surface is lower than the crystal orientation degree of the main phase particle in the magnet central part.