Li-Zn-Mn-Cu Ferrite Material High-Frequency Impedance
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Solution Overview
Problem
Conventional ferrite materials face challenges in achieving high impedance in the high-frequency band, particularly above 30 MHz, due to low specific resistance and sensitivity to external stress, which limits their use in noise filters and other applications, and are often costly due to the inclusion of Ni.
Innovation Solution
A Li-Zn-Mn-Cu ferrite material with a specific composition, including a high amount of Cu and controlled Mn content, combined with Co oxide, Co hydroxide, or Co carbonate additives, to achieve high impedance and resistance while minimizing magnetostriction and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni-Zn-based ferrite is used to achieve high specific resistance and high impedance at high frequency, then the impedance at 10 MHz or more is improved, but the production cost increases and magnetostriction becomes large causing magnetic characteristics to change under external stress
Solution Approach 1:
The patent changes the chemical composition parameters by replacing Ni with Cu and adjusting the ratios of Li, Zn, Mn, and Cu to achieve the desired balance between specific resistance, magnetostriction, and cost. The composition is defined as Li0.5-xZnxCu0.25-yMnyFe2+0.5x-0.25-yO4 where x and y are controlled within specific ranges to optimize properties
Solution Approach 2:
The patent replaces expensive Ni with cheaper Cu to reduce production cost while maintaining the necessary electrical and magnetic properties for high-frequency noise filtering applications
2Reliability
If Mn-Zn-based ferrite is used to achieve high magnetic permeability and high impedance in kHz band, then the impedance in kHz band is improved, but the specific resistance becomes low causing increased eddy current loss at MHz band
Solution Approach 1:
The patent changes the composition parameters by incorporating Cu and controlling Mn content to increase specific resistance to 106 Ωm or more, thereby reducing eddy current loss at MHz frequencies while maintaining adequate magnetic permeability through the Li-Zn-Mn-Cu system
3Ease of manufacture
If Li-Cu-Zn ferrite with high Mn content is used to achieve low cost and low magnetostriction, then the production cost is reduced, but the initial magnetic permeability is lowered and impedance decreases
Solution Approach 1:
The patent optimizes the Mn content parameter by limiting it to 0.055 or less in the composition Li0.5-xZnxCu0.25-yMnymFe2+0.5x-0.25-yO4, and controls the Cu content at 0.07≤z≤0.22 to maintain both cost-effectiveness and high impedance characteristics at 30 MHz and above
Solution Approach 2:
The patent creates a composite ferrite material system combining Li, Zn, Mn, and Cu elements with specific ratios to achieve a balance between cost, magnetostriction, and high-frequency impedance properties that cannot be obtained with single-element substitutions
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 ferrite material exhibits normalized impedance of 40000 Ω/m or more at 30 MHz and 60000 Ω/m or more at 100 MHz, allowing for efficient noise filtration and miniaturization of coil parts with reduced sensitivity to external stress and lower production costs.
Implementation Method 1
For these noise filters, magnetic impedance of ferrite materials has be utilized
Implementation Method 2
the specific resistance thereof is as low as 1 Ωm and therefore, loss due to eddy current in the ferrites is increased in MHz band
Data Source
AI summary
The invention provides a ferrite material (ferrite sintered body, ferrite powders) having a composition formula of (1-x-y-z)(Li0.5Fe0.5)O.xZnO.y(Mn, Fe)2O3.zCuO, wherein x, y, z, and a satisfy 0.175≦x≦0.29; 0.475≦y≦0.51; 0.07≦z≦0.22; and 0.02≦a≦0.055 in a case of a=Mn/(Mn+Fe). At least one of Co oxide, Co hydroxide, and Co carbonate in an amount of 1 wt. % or less on the basis of CoO may be contained in 100 wt % of the ferrite material. The ferrite material has a normalized impedance ZN of 40000 Ω/m or more at 30 MHz and a normalized impedance ZN of 60000 Ω/m or more at 100 MHz as well as a specific resistance of 106 Ωm or more.