Ferrite Sintered Magnet Subphase Design for Coercive Force
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Solution Overview
Problem
Ferrite sintered magnets used in motors and generators face challenges in reducing installation space while maintaining magnetic performance, particularly due to concerns about degaussing and coercive force when thickness is decreased.
Innovation Solution
A ferrite sintered magnet with a hexagonal magnetoplumbite type crystalline structure, incorporating a main phase and subphases with specific atomic ratios of La, Ca, Si, B, and Fe, and containing CaB2O4 to enhance coercive force and magnetic separation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the ferrite sintered magnet is decreased to reduce installation space, then the installation space is reduced, but the coercive force decreases and the magnet becomes susceptible to degaussing
Solution Approach 1:
The patent applies local quality by creating distinct subphases with different compositions at specific locations within the magnet structure. The first subphase (La-rich) and second subphase (Ca-rich with B and Si) are distributed locally among the main phase particles, providing enhanced magnetic separation effects and coercive force improvement in critical regions without requiring overall thickness increase.
Solution Approach 2:
The patent employs composite materials by combining the main phase (AFe12O19 with A=La, Ca, Co) with two distinct subphases having different chemical compositions. The first subphase contains La, Ca, and Fe with La>Ca, while the second subphase contains La, Ca, Si, B, and Fe with specific ratios. This composite structure synergistically improves coercive force and magnetic performance while maintaining reduced dimensions.
2Reliability
If various elements are added to improve Br and HcJ, then the magnetic performance is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atomic ratios of multiple elements within specific ranges. The main phase follows AFe12O19 with A=La, Ca, Co where La+Co>Ca and La>Ca. The first subphase has La>Ca atomic ratios, and the second subphase has B>Fe atomic ratios. These parameter specifications optimize magnetic performance while providing clear manufacturing guidelines.
Solution Approach 2:
The patent distributes different elemental compositions locally within the structure. The first subphase (La-rich) and second subphase (Ca-rich with B and Si) are positioned at grain boundaries and particle interfaces, providing localized enhancement of magnetic properties without uniformly complicating the entire material composition.
Data Source
AI summary
A ferrite sintered magnet contains a main phase formed of ferrite having a hexagonal magnetoplumbite type crystalline structure; a first subphase containing La, Ca, and Fe, in which an atomic ratio of La is higher than that of the main phase, and the atomic ratio of La is higher than an atomic ratio of Ca; and a second subphase containing La, Ca, Si, B, and Fe, in which an atomic ratio of Ca is higher than an atomic ratio of La, an atomic ratio of B is higher than an atomic ratio of Fe, and the atomic ratio of Fe is lower than that of the main phase. An area ratio of the second subphase on a cross-sectional surface of the ferrite sintered magnet is greater than or equal to 1%.