Sm-Fe-N Magnet Powder Crystallinity for High Coercivity
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Solution Overview
Problem
Existing methods for producing Sm—Fe—N-based magnets result in a decrease in saturation magnetization when pulverizing the powder to achieve high coercivity, due to lattice strain and lowered crystallinity, which is not effectively addressed by existing technologies.
Innovation Solution
Control the average particle size of Sm—Fe—N-based magnet powder to not exceed 5 μm and maintain a full width at half maximum of the (220) plane in X-ray diffraction profile to not exceed 0.0033 Å, and sinter under an oxygen concentration not exceeding 10 ppm to prevent decreases in saturation magnetization while maintaining high coercivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the Sm—Fe—N-based magnet coarse powder is pulverized to reduce particle size for achieving high coercivity, then the coercivity is improved, but the saturation magnetization decreases due to lattice strain and lowered crystallinity
Solution Approach 1:
The invention changes the pulverization parameters by controlling the full width at half maximum (FWHM) of the (220) plane diffraction peak to 0.0033 Å or less, which corresponds to maintaining a specific crystallinity level. This parameter control allows achieving high coercivity through fine particle size while preventing excessive lattice strain that would reduce saturation magnetization
Solution Approach 2:
The invention performs preliminary pulverization to reduce particle size to 5 μm or less before sintering, but controls the process to maintain crystallinity. This preliminary action prepares the powder for high coercivity while the controlled crystallinity preservation prevents saturation magnetization loss
2Stability of the object's composition
If the pulverized powder is subjected to heat treatment to remove pulverization strain and improve crystallinity, then the crystallinity is improved, but the coercivity decreases due to oxidation reactions
Solution Approach 1:
The invention performs preliminary pulverization with controlled particle size and crystallinity maintenance before sintering. By optimizing the pulverization process to achieve the target FWHM value, the need for post-pulverization heat treatment is eliminated, thus avoiding oxidation that would reduce coercivity
Solution Approach 2:
The invention extracts the harmful heat treatment step from the process flow. By achieving the desired crystallinity directly through controlled pulverization, the heat treatment step that causes oxidation and coercivity loss is removed from the manufacturing process
3Force
If the Sm—Fe—N-based magnet powder is pulverized to very fine particle size to achieve high coercivity, then the coercivity increases, but the saturation magnetization is notably decreased
Solution Approach 1:
The invention identifies and controls the critical parameter of FWHM of the (220) plane diffraction peak at 0.0033 Å or less. This specific parameter control enables achieving the optimal balance between particle size for high coercivity and crystallinity for maintaining saturation magnetization
Solution Approach 2:
The invention replaces aggressive mechanical pulverization that causes excessive lattice strain with a controlled pulverization process monitored by diffraction peak analysis. This substitution of mechanical intensity control with analytical parameter control prevents saturation magnetization loss while achieving fine particle size
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 solution effectively maintains saturation magnetization at nearly unchanged levels while achieving high coercivity in both the magnet powder and sintered magnets, with saturation magnetization decrease ratios less than 1% and coercivity exceeding 4 kOe.
Implementation Method 1
a method for producing a Sm—Fe—N-based sintered magnet, comprises pressure-sintering a Sm—Fe—N-based magnetic material powder under an atmosphere of an oxygen concentration of not larger than 10 ppm
Implementation Method 2
a full width at half maximum of a diffraction peak of a (220) plane in an X-ray diffraction profile of the Sm—Fe—N-based magnetic material powder is not larger than 0.0033 Å
Data Source
AI summary
A Sm—Fe—N-based magnet powder that includes a Sm—Fe—N-based magnetic material powder, wherein an average particle size of the Sm—Fe—N-based magnetic material powder is not larger than 5 μm, and a full width at half maximum of a diffraction peak of a (220) plane in an X-ray diffraction profile of the Sm—Fe—N-based magnetic material powder is not larger than 0.0033 Å. Also disclosed is a Sm—Fe—N-based sintered magnet that includes a sintered body of a Sm—Fe—N-based magnetic material, wherein an average grain size of crystal grains of the Sm—Fe—N-based magnetic material is not larger than 5 μm, and a full width at half maximum of a diffraction peak of a (220) plane in an X-ray diffraction profile of the Sm—Fe—N-based magnetic material is not larger than 0.0033 Å.