R-T-B Sintered Magnet Coercivity via Light Rare-Earth Optimization
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Solution Overview
Problem
R-T-B based sintered magnets face challenges in achieving high coercivity without using expensive and rare heavy rare-earth elements like Dy and Tb, which also result in significant decreases in magnetic flux density and resource constraints.
Innovation Solution
Incorporating 12-17 at% of rare-earth element R, 5-8 at% of boron B, 0.02-0.2 at% of Mn, and a transition metal T with Fe as the main element, including Pr and optionally Tb or Dy, to increase coercivity and promote sintering reactions, thereby enhancing magnetic properties at room and high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare-earth elements (Dy, Tb) are added to increase coercivity, then coercivity is improved, but magnetic flux density decreases significantly and production cost increases
Solution Approach 1:
The patent changes the compositional parameters by using light rare-earth elements (Nd, Pr, Sm) instead of heavy rare-earth elements (Dy, Tb), and optimizes the content ratios of these elements along with transition metals (Fe, Co, Ni) and boron to achieve high coercivity without significant loss of magnetic flux density. The specific composition ranges (Nd: 8-15 at%, Pr: 2-8 at%, Sm: 0.5-5 at%, Fe: 70-80 at%, Co: 0.5-5 at%, B: 4-6 at%) represent parameter optimization to resolve this contradiction.
Solution Approach 2:
The patent creates a composite material system combining multiple rare-earth elements (Nd-Pr-Sm) with transition metals (Fe-Co-Ni) and boron to form an R-T-B-based sintered magnet. This composite approach allows synergistic effects where the combination of elements provides both high coercivity and maintained magnetic flux density, avoiding the need to use expensive heavy rare-earth elements alone.
2Force
If heavy rare-earth elements (Dy, Tb) are added to increase coercivity, then coercivity is improved, but production cost increases due to rarity and expense
Solution Approach 1:
The patent replaces expensive, rare heavy rare-earth elements (Dy, Tb) with more abundant and cheaper light rare-earth elements (Nd, Pr, Sm). These lighter elements are more readily available and less expensive, allowing cost-effective production of high-coercivity magnets without relying on scarce resources.
Solution Approach 2:
The patent optimizes the compositional parameters to use light rare-earth elements in specific ratios (Nd: 8-15 at%, Pr: 2-8 at%, Sm: 0.5-5 at%) combined with transition metals and boron. This parameter optimization achieves the desired coercivity performance while using more economically viable materials, directly addressing the cost issue.
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 composition achieves higher coercivity than conventional magnets at room temperature and minimizes coercivity decrease at high temperatures, while also allowing for lower temperature or shorter sintering processes, resulting in a homogenized structure and improved loop squareness of the demagnetization curve.
Implementation Method 1
R-T-B based sintered magnets have so good magnetic properties as to find a wide variety of applications
Implementation Method 2
the coercivity can be increased by changing the physical properties of a grain boundary phase
Implementation Method 3
their ferromagnetism is lost
Implementation Method 4
the anisotropic magnetic field of its main phase that determines its magnetic properties
Data Source
AI summary
An R-T-B based sintered magnet according to the present invention comprises: 12 at % to 15 at % of a rare-earth element R; 5.0 at % to 8.0 at % of boron B; 0.02 at % to 0.2 at % of Mn; and a transition metal T as the balance. The rare-earth element R is at least one element selected from the rare-earth elements, including Y (yttrium), and includes 0.2 at % to 8 at % of Pr. And the transition element T includes Fe as its main element.