Sintered Ferrite Magnet Composition With Reduced Co Content
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Solution Overview
Problem
Conventional sintered ferrite magnets, such as SrLaCo and CaLaCo, rely heavily on expensive cobalt and lanthanum, making them costly, and reducing Co content while maintaining magnetic properties is challenging, especially with increasing Co prices due to demand in Li-ion batteries.
Innovation Solution
A sintered ferrite magnet with a composition of Ca, R, A, Fe, and Co, where the atomic ratios are adjusted to optimize Co content reduction while maintaining high magnetic properties, using a production method involving calcining, pulverizing, molding, and sintering with specific additives like SiO2 and CaCO3 to form a hexagonal magnetoplumbite structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Co content is reduced in sintered ferrite magnets, then material cost decreases, but magnetic properties deteriorate
Solution Approach 1:
The patent changes the compositional parameters by introducing specific ratios of Ca, Sr, and La elements along with controlled Co content (0.15-0.30 atomic ratio) to achieve optimal magnetic properties with reduced Co. The general formula Ca1-x-yRxAyFe2n-zCoz with specific parameter ranges (0.20≤x≤0.50, 0.15≤y≤0.40, 0.15≤z≤0.30) enables systematic optimization of magnetic properties while reducing Co content compared to conventional magnets
Solution Approach 2:
The patent creates a composite material system combining multiple rare earth elements (Ca, Sr, La) with Fe and Co in a magnetoplumbite structure. This composite approach allows the synergistic effect of different elements to compensate for reduced Co content, maintaining high magnetic properties (Br≥0.40 T, HcJ≥300 kA/m) with lower Co usage than conventional SrLaCo or CaLaCo magnets
2Reliability
If La content is increased to improve magnetic properties, then magnetic properties improve, but material cost increases
Solution Approach 1:
The patent optimizes the La content parameter within the general formula by controlling the ratio x (where 0.20≤x≤0.50) and balancing it with Ca (1-x-y) and Sr (y) contents. This parameter optimization achieves high magnetic properties while avoiding excessive La content, thereby reducing material cost compared to conventional CaLaCo magnets that typically require higher La content (x≥0.30)
3Quantity of substance
If Sr content is increased to reduce cost, then material cost decreases, but magnetic properties deteriorate
Solution Approach 1:
The patent carefully controls the Sr content parameter y (where 0.15≤y≤0.40) in the general formula to achieve an optimal balance. This controlled Sr substitution for Ca provides cost reduction while the specific parameter range ensures that magnetic properties are maintained through the synergistic effect with La and Co, avoiding the property deterioration that occurs with excessive Sr content
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 approach allows for sintered ferrite magnets with magnetic properties comparable to or exceeding conventional SrLaCo and CaLaCo magnets, even with reduced Co content, achieving high performance at lower costs, suitable for various applications like motors.
Implementation Method 1
calcining the resultant raw material powder mixture
Implementation Method 2
sintering the resultant green body
Data Source
AI summary
A sintered ferrite magnet having a composition of metal elements of Ca, R, A, Fe and Co, which is represented by the general formula of Ca1-x-yRxAyFe2n-zCoz, wherein R is at least one of rare earth elements indispensably including La; A is Sr and/or Ba; x, y, z and n represent the atomic ratios of Ca, R, A, Fe and Co; and 2n represents a molar ratio expressed by 2n = (Fe + Co)/(Ca + R + A), characterized in that x, y, z and n meet the conditions of 0.15 ≤ x ≤ 0.35, 0.05 ≤ y ≤ 0.40, (1 - x -y) > y, 0 < z ≤ 0.18, and 7.5 ≤ (2n - z) < 11.0.