R-T-B Permanent Magnet Grain Boundary Structure for Higher Coercivity
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Solution Overview
Problem
R-T-B based permanent magnets have low coercivity due to magnetization reversal occurring near grain boundaries, and while adding heavy rare-earth elements like Dy increases coercivity, it raises manufacturing costs due to their high price.
Innovation Solution
Incorporating Zr and Cu into the R-T-B based permanent magnet, with specific concentrations and structures of ZrB2 crystals and R—Cu-rich phases at grain boundaries, to enhance coercivity while reducing the need for heavy rare-earth elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare-earth elements such as Dy are added to increase coercivity, then coercivity increases, but manufacturing cost increases due to high price of heavy rare-earth elements
Solution Approach 1:
The patent applies local quality by creating distinct compositional zones within the microstructure: grain boundary regions contain ZrB2 crystals and R-Cu-rich phases with specific element concentrations, while grain interior regions maintain different compositions. This localized differentiation allows coercivity enhancement at grain boundaries without requiring heavy rare-earth elements throughout the entire material, thus reducing overall manufacturing cost while maintaining magnetic performance.
Solution Approach 2:
The patent employs composite materials by combining multiple phases with distinct functions: ZrB2 crystals provide structural framework and pinning sites at grain boundaries, R-Cu-rich phases contribute to magnetic property optimization, and the main phase grains provide bulk magnetic characteristics. This multi-phase composite structure achieves high coercivity through synergistic interactions between phases, eliminating the need for expensive heavy rare-earth element additions.
2Reliability
If heavy rare-earth elements are added to increase coercivity, then magnetization reversal nucleus occurrence decreases, but the content of heavy rare-earth elements must be reduced to lower cost
Solution Approach 1:
The patent extracts the essential function of heavy rare-earth elements (suppressing magnetization reversal nucleus at grain boundaries) and achieves it through alternative mechanisms: ZrB2 crystals provide structural pinning and the R-Cu-rich phases create local magnetic field distributions that prevent reversal nucleus formation. This extraction allows the system to achieve the same coercivity enhancement without relying on expensive heavy rare-earth elements.
Solution Approach 2:
The patent replaces expensive heavy rare-earth elements with more economical alternatives: ZrB2 crystals and R-Cu-rich phases serve as cost-effective substitutes that perform the same functional role of suppressing magnetization reversal. These alternative phases are formed through controlled solidification and phase separation processes, providing an economically viable solution that maintains high coercivity without heavy rare-earth element dependence.
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
The magnet achieves high coercivity with reduced heavy rare-earth element content, lowering manufacturing costs and maintaining magnetic performance.
Implementation Method 1
an anisotropic magnetic field is likely to increase, and the magnetization reversal nucleus is less likely to occur near the grain boundary, and thus the coercivity (HcJ) increases
Implementation Method 2
magnetization reversal nucleus is likely to occur near a grain boundary of a plurality of crystal grains
Data Source
AI summary
Provided is a permanent magnet including a rare-earth element R (such as Nd), a transition metal element T (such as Fe), B, Zr, and Cu. The permanent magnet contains a plurality of main phase grains including Nd, T, and B, and grain boundary multiple junctions, the one grain boundary multiple junction is a grain boundary surrounded by three or more of the main phase grains, one of the grain boundary multiple junctions contains a ZrB2 crystal and an R—Cu-rich phase including R and Cu, Fe is contained in the ZrB2 crystal, a total concentration of Nd and Pr in the one grain boundary multiple junction containing both the ZrB2 crystal and the R—Cu-rich phase is higher than a total concentration of Nd and Pr in the main phase grain, a concentration of Cu in the one grain boundary multiple junction containing both the ZrB2 crystal and the R—Cu-rich phase is higher than a concentration of Cu in the main phase grain, and a unit of the concentration of each of Nd, Pr, and Cu is atomic %.