Sintered 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 compromise on one characteristic to improve the other, and accessory components can lead to issues like surface precipitation and peeling during motor use.
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 0.15% by mass, Si is 0.3 to 0.94% by mass, and a grain boundary composition that forms silicate glass, stabilizing the structure and improving both Br and HcJ, with an average grain size of 1.0 µm or less and a ratio of larger grains ≤1%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If accessory components are added to improve magnetic characteristics, then Br and HcJ are improved, but reliability and strength may be damaged
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of accessory components. Specifically, it limits CaO to 0.01-2.0% by mass, BaO to 0.01-2.0% by mass, and the combined Na2O and K2O to 0.02-0.15% by mass. These controlled parameter ranges optimize magnetic characteristics while preventing excessive accessory component accumulation that would harm reliability and strength.
Solution Approach 2:
The patent employs composite materials by combining Sr ferrite main crystal grains with controlled amounts of multiple accessory components (CaO, BaO, Na2O, K2O, SiO2, Al2O3, TiO2). This composite structure leverages the beneficial effects of each component on magnetic properties while the controlled composition prevents harmful effects on strength and reliability.
2Quantity of substance
If Br and HcJ are improved through composition control, then magnetic characteristics are enhanced, but reliability may be compromised
Solution Approach 1:
The patent uses parameter changes by establishing specific composition ranges for accessory components. It controls CaO at 0.01-2.0%, BaO at 0.01-2.0%, Na2O+K2O at 0.02-0.15%, SiO2 at 0.3-0.94%, and Al2O3 at 0.01-1.0%. These parameter constraints ensure that magnetic characteristics are improved while reliability is maintained by preventing surface precipitation and peeling.
Solution Approach 2:
The patent introduces SiO2 and Al2O3 as intermediary substances that form a stable grain boundary phase. This intermediary layer mediates between the main crystal grains and accessory components, preventing direct harmful interactions while maintaining magnetic properties and improving reliability by reducing surface precipitation and enhancing structural stability.
3Quantity of substance
If accessory components are used to improve sinterability and magnetic characteristics, then Br and HcJ increase, but surface precipitation and peeling occur
Solution Approach 1:
The patent applies parameter changes by strictly limiting the composition of accessory components that cause surface precipitation. It controls CaO to 0.01-2.0%, BaO to 0.01-2.0%, and Na2O+K2O to 0.02-0.15% by mass. These controlled parameter ranges prevent excessive accessory component accumulation at grain boundaries, thereby eliminating surface precipitation and peeling while maintaining improved magnetic characteristics.
Solution Approach 2:
The patent uses SiO2 (0.3-0.94% by mass) and Al2O3 (0.01-1.0% by mass) as intermediary substances that form a stable grain boundary phase. This intermediary layer prevents direct contact and harmful interactions between accessory components, thereby eliminating surface precipitation and peeling while maintaining the beneficial magnetic properties enhanced by the accessory components.
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 a sintered ferrite magnet with enhanced magnetic characteristics and reliability, achieving high efficiency and reliability in motor applications by maintaining a stable and dense structure, thus improving both Br and HcJ values.
Implementation Method 1
a grain boundary composition that forms silicate glass, stabilizing the structure and improving both Br and HcJ
Data Source
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AI summary
Provided is a sintered ferrite magnet 10 that comprises Sr ferrite having a hexagonal crystal structure, wherein the total amount of Na and K is 0.004 to 0.31% by mass in terms of Na2O and K2O, an amount of Si is 0.3 to 0.94% by mass in terms of SiO2, and the following Expression (1) is satisfied. 1.3≤SrF+Ba+Ca+2Na+2K/Si≤5.7 [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.]