Two-Phase Sintered Ferrite Magnet for High Coercivity
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Solution Overview
Problem
Current sintered ferrite magnets, such as SrLaCo and CaLaCo, do not meet the increasing demand for higher magnetic performance, particularly in coercivity (HcJ) and rectangularity (Hk/HcJ), which are essential for applications like automobile electric parts.
Innovation Solution
A sintered ferrite magnet is produced by mixing calcined CaLaCo and SrLaCo ferrites at a specific ratio, resulting in a unique two-phase structure with distinct Curie temperatures, enhancing HcJ while maintaining high residual magnetic flux density (Br) and Hk/HcJ ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Sr ferrite or Ba ferrite is used as conventional sintered ferrite magnets, then production cost is low, but magnetic properties (coercivity HcJ and residual magnetic flux density Br) are insufficient for high-performance applications
Solution Approach 1:
The patent uses composite materials by combining Sr ferrite and Ba ferrite in specific ratios to create a sintered ferrite magnet with enhanced magnetic properties. The composite structure leverages the complementary characteristics of both ferrite types to achieve high coercivity and residual magnetic flux density while maintaining cost-effectiveness through powder metallurgy processing
2Reliability
If SrLaCo ferrite is used to improve magnetic properties, then coercivity HcJ increases, but rectangularity Hk/HcJ deteriorates
Solution Approach 1:
The patent changes the compositional parameters by introducing Ba ferrite into the SrLaCo ferrite system. By controlling the ratio of Sr ferrite to Ba ferrite and adjusting the substitution levels of La and Co, the patent optimizes both coercivity and rectangularity simultaneously, overcoming the limitation of SrLaCo ferrite alone
3Reliability
If CaLaCo ferrite is used to increase anisotropic field HA, then HA increases by 10% or more, but rectangularity Hk/HcJ becomes extremely poor
Solution Approach 1:
The patent merges SrLaCo ferrite and CaLaCo ferrite in a composite structure. This combination allows the material to benefit from the high anisotropic field of CaLaCo ferrite while the Sr ferrite component maintains adequate rectangularity, achieving a balance between these two critical magnetic properties
4Weight of moving object
If sintered ferrite magnets are made thinner to reduce size and weight, then compactness increases, but demagnetization resistance decreases due to lower coercivity HcJ
Solution Approach 1:
The patent changes the magnetic parameters by optimizing the composite ratio of Sr ferrite and Ba ferrite along with rare earth and transition metal substitutions. This enables achieving high coercivity values that maintain demagnetization resistance even in thin magnet configurations, allowing size reduction without sacrificing performance
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 resulting magnet exhibits improved coercivity and rectangularity, meeting the higher performance requirements for applications like automobile electric parts without significant reduction in magnetic properties.
Implementation Method 1
a sintered ferrite magnet production method comprising: mixing a calcined CaLaCo ferrite and a calcined SrLaCo ferrite at a mass ratio of 90/10 to 50/50 to prepare a mixed calcined ferrite; pulverizing, molding and sintering the mixed calcined ferrite
Data Source
Figure 1~2
Figure 3(a)~3(c)
Figure 3(d)~3(f)
AI summary
A sintered ferrite magnet comprising a first granular ferrite compound phase containing Ca, La, Fe and Co and having a Curie temperature Tc1 between 415°C and 430°C, and a second granular ferrite compound phase containing Sr, La, Fe and Co and having a Curie temperature Tc2 between 437°C and 455°C, the volume ratio of the first ferrite compound phase being 50-90%, and the volume ratio of the second ferrite compound phase being 10-50%, with their total volume ratio being 95% or more.