Ferrite Sintered Magnet Grain Circularity Optimization
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Solution Overview
Problem
Ferrite sintered magnets face challenges in achieving improved residual magnetic flux density (Br) while maintaining high coercive force (HcJ), as existing compositions often result in either reduced Br or decreased HcJ due to the shape and size of ferrite grains.
Innovation Solution
A ferrite sintered magnet with ferrite grains having a hexagonal crystal structure and specific circularity and Heywood diameter ranges, along with a composition including Ca, R, A, Fe, Co, and Mg, is developed to enhance Br while maintaining high HcJ, utilizing a production process involving blending, calcination, pulverization, compacting, and firing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Fe is partly replaced with Mg to improve magnetic properties, then residual magnetic flux density Br is improved, but coercive force HcJ decreases
Solution Approach 1:
The patent optimizes the circularity parameter W of ferrite grains within the range 0.56≤W≤0.68, and controls the average Heywood diameter within 1.00 μm or more and 1.23 μm or less. These parameter changes in grain morphology enable improved Br while maintaining high HcJ, resolving the contradiction between these two magnetic properties.
Solution Approach 2:
The patent uses a composite composition including Ca, R (rare earth elements), A (Ba or Sr), Fe, Co, and Mg in specific ratios. This composite material approach allows the ferrite sintered magnet to achieve both improved Br and maintained HcJ by combining multiple elements with complementary effects.
2Quantity of substance
If ferrite grain shape and size are optimized to improve Br, then manufacturing complexity increases
Solution Approach 1:
The patent defines specific ranges for circularity (0.56≤W≤0.68) and Heywood diameter (1.00-1.23 μm) that can be achieved through standard sintering processes. By specifying attainable parameter ranges rather than idealized shapes, the patent balances Br improvement with manufacturing feasibility.
Data Source
AI summary
A ferrite sintered magnet including ferrite grains having a hexagonal crystal structure. The ferrite grains satisfy 0.56≤W≤0.68 where W is an average value of circularities of the ferrite grains in a cross section parallel to an axis of easy magnetization.