Core-Shell R-T-B Magnet Coercivity via Localized Heavy Rare Earth
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Solution Overview
Problem
Conventional R-T-B based sintered magnets experience demagnetization at high temperatures, requiring improved coercivity to maintain magnetic performance in applications like hybrid vehicles.
Innovation Solution
The development of a rare earth-based permanent magnet with a sintered compact containing main phase grains of R-T-B composition, featuring a core-shell structure with specific concentration distributions of rare earth elements, which increases coercivity by generating a pinning effect on magnetic domain walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements (Dy, Tb, Ho) are added to increase coercivity, then coercivity is improved, but resource consumption increases and cost increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell region has a different composition (higher heavy rare earth element concentration) than the core region. This localized distribution of heavy rare earth elements in the shell provides the necessary coercivity enhancement at the grain boundaries while minimizing the overall amount of heavy rare earth elements used in the magnet.
Solution Approach 2:
The patent uses composite materials by combining light rare earth elements (R1: Nd, Pr, La, Ce, Sm) with heavy rare earth elements (R2: Dy, Tb, Ho) in a specific core-shell configuration. The composite structure of R1-T-B core and R1-R2-T-B shell creates synergistic effects that improve coercivity while controlling heavy rare earth element consumption.
2Reliability
If heavy rare earth elements are added to increase coercivity, then coercivity is improved, but manufacturing cost increases
Solution Approach 1:
By concentrating heavy rare earth elements in the shell region rather than uniformly distributing them throughout the magnet, the patent reduces the total amount of expensive heavy rare earth elements required. This localized approach maintains coercivity performance while significantly reducing material costs.
Solution Approach 2:
The patent optimizes the concentration parameters of heavy rare earth elements in the shell region (typically 1-5 atomic percent R2 in the shell) to achieve the desired coercivity with minimal heavy rare earth element content. This parameter optimization balances performance requirements with cost constraints.
3Adaptability or versatility
If the magnet is used in high temperature environments, then application versatility is improved, but demagnetization occurs due to reduced coercivity at high temperature
Solution Approach 1:
The core-shell structure with heavy rare earth element enrichment in the shell provides enhanced thermal stability. The shell region acts as a protective layer that maintains magnetic properties at elevated temperatures, enabling the magnet to withstand high temperature environments without demagnetization.
Solution Approach 2:
The composite R1-T-B and R1-R2-T-B phases in the core-shell structure create a material system with improved thermal stability. The heavy rare earth elements in the shell suppress thermal agitation of magnetic moments, maintaining coercivity at high temperatures and enabling versatile applications in hybrid vehicles and industrial equipment.
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 coercivity and prevents magnetic coupling between grains, maintaining high residual magnetic flux density while minimizing the use of heavy rare earth elements, thus addressing the issue of demagnetization at high temperatures.
Implementation Method 1
The present invention provides a rare earth based permanent magnet with a sintered compact containing main phase grains of an R-T-B based composition, featuring a core-shell structure with specific concentration distributions of rare earth elements, which increases coercivity by generating a pinning effect on magnetic domain walls.
Implementation Method 2
The R-T-B based sintered magnet with the rare earth element(s) R being composed of Nd, Pr, Dy, Tb and/or Ho has a large magnetic anisotropy field Ha and is preferably used as a permanent magnet material.
Data Source
AI summary
A rare earth based permanent magnet has a sintered compact with R-T-B based composition. The compact has two kinds of main phase grains M1 and M2 having different concentration distributions of R including R1 and R2 respectively representing at least one rare earth element including Y and excluding Dy, Tb and Ho, and at least one from Ho, Dy and Tb. M1 and M2 have a core-shell structure containing a shell part coating a core part. In M1, when the R1 and R2 atom concentrations in the core and shell parts are defined as αR1, αR2, βR1 and βR2, respectively, αR1>βR1, αR2<βR2, αR1>αR2 and βR1<βR2. In M2, when the R1 and R2 atom concentrations in the core and shell parts are defined as γR1, γR2, εR1 and εR2, respectively, γR1<εR1, γR2>εR2, γR1<γR2 and εR1>εR2. Ratios occupied by the main phase grains having the core-shell structure are 5% or more, respectively.