Ferrite Sintered Magnet Composition for Thin Stable Firing
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Solution Overview
Problem
Existing ferrite sintered magnets face challenges in achieving excellent magnetic properties and production stability, especially when thin, due to variations in composition and firing temperature, which affect coercive force and residual magnetic flux density.
Innovation Solution
A ferrite sintered magnet with a specific atomic ratio of A1−xRx(Fe12−yCoy)zO19, where A includes Sr, Ba, or Pb, R is La or rare earth elements, and controlled CaO and SiO2 content, is developed, with a firing process optimizing the green compact thickness between 3.5 to 8.0 mm to maintain high magnetic properties and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high Co content is used to improve coercive force, then magnetic properties are improved, but production stability deteriorates due to sensitivity to composition and firing temperature variations
Solution Approach 1:
The patent changes the chemical composition parameters by reducing Co content from conventional high levels to 0.5-2.0 mass%, while precisely controlling CaO (0.8-1.5 mass%) and SiO2 (0.3-0.8 mass%) contents. This parameter optimization reduces sensitivity to firing temperature variations and improves production stability while maintaining high coercive force
Solution Approach 2:
The patent creates a composite ferrite system combining Sr ferrite base material with specific rare earth elements (Nd, Dy, Tb) and controlled amounts of Co, Ca, and Si. This composite approach allows the rare earth elements to provide magnetic strengthening while the controlled Co content and CaO-SiO2 system provide structural stability, reducing overall Co dependency
2Volume of moving object
If thin magnet design is implemented to reduce size, then compactness is improved, but production stability deteriorates due to difficulty in maintaining uniform properties
Solution Approach 1:
The patent optimizes the green compact thickness parameter to 3.5-8.0 mm before firing, which provides sufficient structural integrity for thin magnets while ensuring uniform heat distribution during firing. This parameter control enables production of thin sintered magnets (2.0-6.0 mm) with stable magnetic properties
Solution Approach 2:
The patent performs preliminary forming of the green compact with controlled thickness and density uniformity before firing. This preliminary action ensures that the green compact has uniform structure and dimensions, which translates to uniform sintered magnet properties even when the final thickness is small (2.0-6.0 mm)
3Reliability
If high Br is achieved through composition optimization, then residual magnetic flux density is improved, but manufacturing complexity increases due to precise composition control requirements
Solution Approach 1:
The patent identifies and optimizes key composition parameters: rare earth element content (0.5-3.0 mass%), Co content (0.5-2.0 mass%), CaO content (0.8-1.5 mass%), and SiO2 content (0.3-0.8 mass%). By focusing control on these specific parameters within defined ranges, the patent achieves high Br (1.2-1.6 T) while keeping manufacturing complexity manageable through clear specification limits
Solution Approach 2:
The patent applies different compositional strategies to different functional requirements: rare earth elements and Co are optimized for magnetic properties (Br), while CaO and SiO2 are optimized for sintering behavior and microstructure. This local quality approach allows independent optimization of magnetic performance and manufacturing ease
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 results in ferrite sintered magnets with improved coercive force, residual magnetic flux density, and production stability, while reducing costs by minimizing excess Co content and maintaining magnetic properties across varying thicknesses and firing temperatures.
Implementation Method 1
a ferrite sintered magnet having excellent magnetic properties, a high residual magnetic flux density Br or a high coercive force HcJ, it is known to use an Sr ferrite which is a hexagonal M-type ferrite
Implementation Method 2
ferrite sintered magnet and manufacturing method therefor
Data Source
AI summary
A ferrite sintered magnet represented by A1−xRx(Fe12−yCoy)zO19 in terms of atomic number ratio. A is at least one selected from a group made of Sr, Ba and Pb. R is La only or La and at least one selected from a group made of Bi and rare earth elements. 0.14≤x≤0.22, 11.60≤(12−y)×z≤11.99, and 0.13≤y×z≤0.17 are satisfied. 0.500≤Mc≤0.710 is satisfied in which Mc is CaO content in mass % converted from a content of Ca included in the ferrite sintered magnet. 0.410≤Ms≤0.485 is satisfied in which Ms is SiO2 content in mass % converted from a content of Si included in the ferrite sintered magnet.