Sr Ferrite Magnet Grain Boundary Silicate Glass
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Solution Overview
Problem
Sintered ferrite magnets face challenges in simultaneously enhancing both residual magnetic flux density (Br) and coercive force (HcJ) while maintaining reliability and strength, as existing methods often result in a trade-off between these characteristics and can be compromised by accessory components.
Innovation Solution
A sintered ferrite magnet with a hexagonal crystal structure, specifically formulated with Sr ferrite, where the total amount of Na and K is 0.02 to 0.09% by mass, Si is 0.1 to 0.29% by mass, and a silicate glass is formed at the grain boundary, stabilizing the structure and improving both Br and HcJ, with an average grain size of 1.0 µm or less and a specific composition ratio that enhances reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If accessory components are added to improve magnetic characteristics, then Br and HcJ are improved, but strength and external appearance reliability are damaged
Solution Approach 1:
The invention optimizes the compositional parameters of accessory components, specifically limiting total Na and K to 0.01-0.10% by mass and Si to 0.05-0.30% by mass. This parameter control allows the accessory components to provide magnetic benefits while preventing excessive degradation of mechanical strength and external appearance.
Solution Approach 2:
The invention creates a composite structure where Sr ferrite main crystal grains are combined with controlled amounts of specific accessory components (Na, K, Si). This composite approach allows the accessory components to form a grain boundary phase that improves magnetic characteristics (Br and HcJ) while the controlled composition prevents harmful effects on strength and external appearance.
2Reliability
If accessory components are added to improve magnetic characteristics, then Br and HcJ are improved, but foreign matter precipitation on surface occurs
Solution Approach 1:
The invention严格控制 the compositional parameters of accessory components, particularly limiting Si to 0.05-0.30% by mass and total Na and K to 0.01-0.10% by mass. This parameter optimization prevents excessive foreign matter precipitation on the magnet surface while maintaining improved magnetic characteristics.
Solution Approach 2:
The accessory components are strategically localized at the grain boundaries between Sr ferrite crystal grains, forming a grain boundary phase. This local concentration allows the accessory components to improve magnetic characteristics at the grain boundary regions without causing widespread foreign matter precipitation on the external surface.
3Reliability
If Br and HcJ are both improved, then magnetic characteristics are enhanced, but trade-off relationship limits further improvement
Solution Approach 1:
The invention optimizes specific compositional parameters (total Na and K: 0.01-0.10% by mass, Si: 0.05-0.30% by mass) to achieve simultaneous improvement in both Br and HcJ. By focusing on these specific parameter ranges, the invention overcomes the traditional trade-off relationship between Br and HcJ.
Solution Approach 2:
The accessory components (Na, K, Si) act as intermediaries that modify the grain boundary phase between Sr ferrite crystal grains. This intermediary phase facilitates simultaneous improvement of both Br and HcJ by affecting both magnetization and coercivity mechanisms, thereby breaking the traditional trade-off relationship.
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 achieves high magnetic characteristics and reliability, with a calculated value of Br + 1/3HcJ ≥ 5.2, ensuring the sintered ferrite magnet is suitable for motor applications with improved efficiency and reliability.
Implementation Method 1
a silicate glass is formed at the grain boundary, stabilizing the structure and improving both Br and HcJ
Data Source
Figure 1
Figure 2
AI summary
Provided is a sintered ferrite magnet 10 that contains Sr ferrite having a hexagonal crystal structure, wherein the total amount of Na and K is 0.01 to 0.09% by mass in terms of Na2O and K2O, an amount of Si is 0.1 to 0.29% by mass in terms of SiO2, and the following Expression (1) is satisfied. [In Expression (1), SrF represents an amount of Sr, on a molar basis, other than Sr which constitutes the Sr ferrite, and Ba, Ca, Na, and K represent amounts of respective elements on a molar basis.]