R-T-B Permanent Magnet Ce Surface Gradient for Adhesion
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Solution Overview
Problem
R-T-B based permanent magnets with Ce or Y as rare earth elements face challenges in maintaining high magnetic properties, particularly coercive force, while achieving high adhesive strength, which is crucial for applications in surface magnet-type rotating machines.
Innovation Solution
The R-T-B based permanent magnet incorporates a composition of (R1-x(Ce1-zYz)2T14B, where R includes rare earth elements like La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, with Ce and Y selectively replacing Nd at specific lattice positions, adjusting the valence and ionic radius to enhance adhesive strength without significantly reducing magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ce or Y is used as the rare earth element R in the R-T-B based permanent magnet, then adhesive strength is improved, but magnetic properties (coercive force) deteriorate
Solution Approach 1:
The patent applies local quality by creating distinct regions with different Ce concentrations. The surface region has higher Ce content (0.05-0.20 mass%) to provide strong adhesive strength through cubic oxide formation, while the inner region maintains lower Ce content (0.01-0.06 mass%) to preserve high coercive force and magnetic properties. This spatial differentiation of composition resolves the contradiction between adhesive strength and magnetic performance.
Solution Approach 2:
The patent utilizes parameter changes by controlling the cooling rate during solidification to manipulate Ce distribution. By adjusting the cooling rate, Ce is selectively concentrated at the surface region while maintaining appropriate levels in the inner region. This parameter control enables simultaneous achievement of high adhesive strength (from surface Ce oxides) and high coercive force (from inner region composition).
2Reliability
If high purity Nd is used to maintain high magnetic properties, then coercive force is improved, but cost increases
Solution Approach 1:
The patent employs this principle by using commercially available Nd with Ce impurity (0.03-0.08 mass% Ce) instead of expensive high-purity Nd. The controlled solidification process transforms the previously harmful Ce impurity into a beneficial surface modification that enhances adhesive strength. This approach eliminates the need for costly high-purity materials while maintaining or improving overall performance.
Solution Approach 2:
The patent converts the harmful effect of Ce impurity (which reduces coercive force when uniformly distributed) into a beneficial surface modification. By controlling solidification, Ce is concentrated at the surface where it forms cubic oxides that enhance adhesive strength, while the bulk material retains sufficient Nd content to maintain high coercive force. This transforms a material defect into a performance advantage.
3Volume of moving object
If surface magnet type configuration is used, then space utilization is improved, but adhesive reliability deteriorates due to centrifugal force
Solution Approach 1:
The patent applies local quality by creating a surface region with enhanced adhesive properties through Ce concentration. This surface region (0.05-0.20 mass% Ce) forms strong cubic oxide bonds that resist centrifugal force, while the inner region maintains magnetic performance. This localized surface modification enables surface magnet type configuration to achieve both compact design and high adhesive reliability under rotation.
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 results in a permanent magnet with high adhesive strength and maintained magnetic properties comparable to Nd—Fe—B based magnets, effectively addressing the issue of coercive force and adhesive strength in surface magnet-type rotating machines.
Implementation Method 1
Ce and Y selectively replacing Nd at specific lattice positions, adjusting the valence and ionic radius to enhance adhesive strength
Implementation Method 2
Many cubic systems whose interaxial angle is an acute angle as compared with other crystal systems such as hexagonal system and the like, generate an anchoring (adhering) effect on the surface of an oxidized R-T-B based permanent magnet
Data Source
AI summary
A R-T-B based permanent magnet which not only has equivalent magnetic properties as the existing Nd—Fe—B based permanent magnet but also has a high adhesive strength and which can be suitably used as a magnet for field system of a permanent magnet synchronous rotating machine. The magnet can be obtained in a case where the composition of the compound for forming the main phase is (R1-x(Ce1-zYz)x)2T14B (R is rare earth element(s) consisting of one or more elements selected from La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, T is one or more transition metal elements with Fe or Fe and Co as essential element(s), 0.0<x≦0.5 and 0.0≦z≦0.5), by making the abundance ratio of Ce4f/(Ce4f+Ce4g) satisfies 0.8≦Ce4f/(Ce4f+Ce4g)≦1.0 when the Ce occupying the 4f site of the tetragonal R2T14B structure is denoted Ce4f and the Ce occupying the 4g site is denoted as Ce4g.