Sintered R-T-B Magnet Composition for Br and ET Coercivity Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing R-T-B sintered magnets face challenges in achieving high remanence (Br) and elevated temperature stability (ET stability) while maintaining room temperature coercivity (RT coercivity), with previous methods either compromising RT coercivity or being difficult to scale in mass production due to stringent cooling rate requirements.
Innovation Solution
A R-T-B sintered magnet composition is optimized with a main phase of R2Fe14B and a grain boundary phase containing R-T-(M1, M2) and R-M2-C phases, with specific atom concentrations and the inclusion of elements like Sn and C, which helps in forming a R-M2-C phase that anchors C and suppresses the drop of RT coercivity, thereby achieving high Br and ET stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Sn is added to improve ET stability, then ET coercivity is enhanced, but RT coercivity drops
Solution Approach 1:
The patent optimizes the Sn content parameter within a specific range (0.01-0.5 atom%) to balance ET stability improvement while minimizing RT coercivity drop. It also adjusts the ratio of M1 to M2 elements and controls the composition of R-T-(M1, M2) and R-M2-C phases to achieve optimal magnetic properties at both temperatures.
Solution Approach 2:
The patent creates a composite grain boundary phase structure containing both R-T-(M1, M2) and R-M2-C phases with specific composition ratios. This composite structure allows the Sn-containing R-M2-C phase to improve ET stability while the overall composition design maintains RT coercivity by controlling the distribution and concentration of different phases.
2Reliability
If heavy rare earth elements like Dy and Tb are substituted to improve HcJ, then magnetocrystalline anisotropy increases, but resource availability decreases
Solution Approach 1:
The patent replaces expensive and scarce heavy rare earth elements (Dy, Tb) with lighter, more abundant elements like Sn, Si, Ge, In, and Pb. These substitute elements achieve comparable or superior coercivity improvement through the formation of R-M2-C phases and modification of grain boundary structure, making the magnet more resource-sustainable.
Solution Approach 2:
The patent changes the compositional parameters by introducing M2 elements (Sn, Si, Ge, In, Pb) at controlled concentrations (0.01-0.5 atom%) to replace heavy rare earth elements. This substitution strategy maintains or enhances coercivity through different mechanisms (grain boundary phase formation, crystal structure modification) while avoiding resource scarcity issues.
3Reliability
If main phase crystal grain size is reduced to enhance HcJ, then coercivity improves, but manufacturing complexity increases
Solution Approach 1:
The patent introduces M2 elements (Sn, Si, Ge, In, Pb) as intermediary substances that form R-M2-C phases at grain boundaries. These intermediary phases mediate the grain boundary structure and properties, enabling coercivity enhancement through chemical composition control rather than relying solely on precise grain size control, thereby simplifying manufacturing.
Solution Approach 2:
The patent shifts the control parameter from physical grain size to chemical composition (M2 element content and phase ratio). By controlling the concentration of M2 elements and the composition of grain boundary phases within specific ranges, the patent achieves coercivity enhancement through compositional optimization rather than stringent structural control, reducing manufacturing complexity.
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 optimized composition results in a R-T-B sintered magnet with high Br and satisfactory ET stability, effectively addressing the limitations of previous methods by maintaining high RT coercivity and ET stability without significant drops in magnetic properties.
Implementation Method 1
the inclusion of elements like Sn and C, which helps in forming a R-M2-C phase that anchors C and suppresses the drop of RT coercivity
Data Source
AI summary
A R-T-B sintered magnet comprising a main phase of R2Fe14B and a grain boundary phase exhibits a high Br and elevated-temperature stability. The magnet is composed of 12.5-17.0 atom % of R which is typically Nd and Pr, 4.5-5.5 atom % of B, at least 70 atom % of T which is Fe and Co, 0.1-3.0 atom % of M1 which is typically Al, Cu or Ga, 0.01-0.5 atom % of M2 which is typically Sn, 0.05-1.0 atom % of M3 which is typically Zr, and up to 0.8 atom % of O, and the balance of C, N and incidental impurities. The grain boundary phase contains a R-T-(M1, M2) phase and a R-M2-C phase.