R-T-B Rare Earth Magnet B Content Optimization
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Solution Overview
Problem
R-T-B based rare earth magnets face challenges in achieving improved magnetic properties and a wide optimal temperature range for sintering due to instability in B content and reaction of high melting point compounds during the sintering process.
Innovation Solution
The R-T-B based rare earth magnet is formulated with a B content of 0.80 to 0.98 mass % and includes an R1T4B4 phase, which stabilizes magnetic properties and sintering temperature, and may incorporate a concentration gradient of heavy rare earth elements to enhance coercive force and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the B content is lowered below the stoichiometric ratio to reduce B-rich phase formation, then the residual magnetic flux density is improved, but the property stability is lowered and the sintering temperature range is narrowed
Solution Approach 1:
The patent applies parameter changes by precisely controlling the B content within a specific range (0.80-0.98 mass%) rather than simply lowering it below stoichiometric ratio. This quantitative parameter optimization resolves the contradiction by finding the optimal balance point where sufficient B is present to maintain property stability and wide sintering temperature range, while enough B-rich phase is suppressed to achieve high residual magnetic flux density.
2Stability of the object's composition
If a compound of heavy rare earth element with high melting point is added to improve property stability, then the sintering temperature range is widened, but the compound reacts with liquid phase and melts down during sintering, reducing the stabilizing effect
Solution Approach 1:
The patent changes the compositional parameters by incorporating heavy rare earth elements (Dy, Tb) at optimized concentrations (0.1-2.0 mass% each) within the R2T14B phase structure. This compositional optimization allows the heavy rare earth elements to stabilize the magnetocrystalline anisotropy and widen the sintering temperature range without requiring separate high-melting-point compounds that would react with the liquid phase.
Solution Approach 2:
The patent creates a composite phase structure where heavy rare earth elements are integrated into the R2T14B main phase, forming a composite material system that combines the high coercivity of heavy rare earth elements with the magnetic properties of the R2T14B phase. This integrated composite structure eliminates the need for separate stabilizing compounds while maintaining property stability across a wide sintering temperature range.
Data Source
AI summary
Provided is an R-T-B based rare earth magnet. R is one or more rare earth elements, T is one or more transition metal elements essentially including Fe or Fe and Co, and B is boron. B content with respect to a total R-T-B based rare earth magnet is 0.80 mass % or more and 0.98 mass % or less. The R-T-B based rare earth magnet includes an R1T4B4 phase.