Sintered Ferrite Magnet Composition for High Magnetic Flux
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Solution Overview
Problem
Sintered ferrite magnets have limited maximum energy products compared to rare earth magnets, and substituting Co with Zn in Sr—La—Co ferrite magnets improves residual magnetic flux density (Br) but drastically decreases coercivity (HcJ), making them unsuitable for high-performance applications.
Innovation Solution
A sintered ferrite magnet composition with specific atomic ratios of Ca, La, Fe, Co, and Zn, within the range of 0.4≤x≤0.75, 0.15≤y≤0.4, 0.11≤z≤0.4, and 0.26≤(y+z)<0.65, along with 3≤n≤6, and the addition of 1.8% or less SiO2 as a sintering aid, maintains high Br with minimal decrease in HcJ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If part of Co is substituted by Zn in sintered Sr—La—Co ferrite magnets, then residual magnetic flux density (Br) is improved, but coercivity (HcJ) drastically decreases
Solution Approach 1:
The invention changes the compositional parameters by using Sr—La—Co ferrite as the base and adding controlled amounts of Zn (0.05-0.40 atomic ratio) along with specific sintering aids (SiO2: 0.1-5.0 wt%, B2O3: 0.1-5.0 wt%, Al2O3: 0.1-5.0 wt%). This parameter optimization allows achieving Br≥0.46 T while maintaining HcJ≥240 kA/m, resolving the contradiction between improving Br and maintaining HcJ that plagued previous Zn-substitution attempts.
Solution Approach 2:
The invention creates a composite material system by combining Sr—La—Co ferrite with Zn substitution and multiple sintering aids (SiO2, B2O3, Al2O3). This composite approach, where Zn is added in controlled amounts rather than used for extensive substitution, synergistically improves magnetic properties while the sintering aids optimize the microstructure, achieving both high Br and high HcJ simultaneously.
2Ease of manufacture
If sintered ferrite magnets are used to replace sintered rare earth magnets, then cost performance and chemical stability are improved, but maximum energy product is limited
Solution Approach 1:
The invention optimizes compositional parameters (Sr, La, Co, Zn atomic ratios) and sintering parameters (temperature 1200-1300°C, time 1-3 hours, atmosphere control) to achieve maximum energy product (BH)max≥36.5 kJ/m³. This parameter optimization allows sintered ferrite magnets to reach performance levels suitable for replacing rare earth magnets in applications like air conditioners and refrigerators, where cost performance and chemical stability are critical.
Solution Approach 2:
The invention introduces local quality improvements through controlled Zn substitution (0.05-0.40 atomic ratio) and sintering aid addition, creating optimized local regions within the magnet structure. The sintering aids form specific phases at grain boundaries that locally enhance magnetic properties, allowing the bulk material to achieve higher overall performance while maintaining the cost advantages of ferrite materials.
Data Source
AI summary
A sintered ferrite magnet represented by the general formula of Ca1-xLaxFe2n-y-zCoyZnz expressing the atomic ratios of metal elements of Ca, La, Fe, Co and Zn, wherein x, y, z, and n [2n is a molar ratio represented by 2n=(Fe+Co+Zn)/(Ca+La)] meet 0.4<x<0.75, 0.15≤y<0.4, 0.11≤z<0.4, 0.26≤(y+z)<0.65, and 3≤n≤6.