Mn-Zn-Co Ferrite for Stable Permeability in Small Cores
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Solution Overview
Problem
Mn—Zn ferrite magnetic cores for pulse transformers in Ethernet devices face challenges in maintaining high incremental permeability across a wide temperature range due to temperature-dependent magnetic characteristics and issues with compaction pressure leading to cavity formation in small core sizes, which reduces permeability.
Innovation Solution
A Mn—Zn—Co ferrite composition with specific ranges of iron oxide, zinc oxide, cobalt oxide, and manganese oxide, along with added silicon oxide, calcium oxide, and reduced impurities such as phosphorus, boron, sulfur, and chlorine, to suppress exaggerated grain growth and enhance domain wall motion, ensuring high incremental permeability even in small core sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Mn—Zn ferrite is used to achieve high permeability and high inductance, then the material cost is reduced compared to amorphous metals, but the magnetic characteristics vary considerably with temperature change
Solution Approach 1:
The patent uses a composite material approach by combining Mn—Zn ferrite with CoO (cobalt oxide) to create a Mn—Zn—Co ferrite system. The CoO component with positive magnetic anisotropy compensates for the temperature-dependent variations in the Mn—Zn ferrite base material, thereby stabilizing the magnetic characteristics across a wide temperature range while maintaining the cost advantages of ferrite materials.
Solution Approach 2:
The patent modifies the chemical composition parameters of the ferrite material by adding specific amounts of CoO (0.04 to 0.60 mol %) to the Mn—Zn ferrite system. This parameter change in composition alters the magnetic anisotropy characteristics, enabling the material to maintain stable incremental permeability (μΔ ≥ 2000) from -40°C to 85°C under a DC magnetic field of 33 A/m.
2Volume of moving object
If small core size (outer diameter 2 to 6 mm) is used for pulse transformer application, then the device compactness is improved, but cavity formation occurs due to insufficient disintegration of granulated powder under compaction
Solution Approach 1:
The patent applies preliminary action by pre-disintegrating the granulated powder to an appropriate degree before compaction. This preliminary disintegration ensures that the powder particles are sufficiently broken down to fill cavities during the compaction process, preventing void formation in the small core structure while maintaining the compact size requirements for Ethernet device applications.
3Manufacturing precision
If high compaction pressure is applied to small core size, then the density and manufacturing precision are improved, but mold breakage probability increases
Solution Approach 1:
The patent applies preliminary action by pre-disintegrating the granulated powder to an appropriate degree before compaction. This preliminary disintegration ensures that the powder particles are sufficiently broken down to fill cavities during the compaction process, preventing void formation in the small core structure while maintaining the compact size requirements for Ethernet device applications.
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 achieves continuous incremental permeability of 2000 or more in a wide temperature range of −40° C. to 85° C. under a direct-current magnetic field, improving the stability and performance of magnetic cores in Ethernet devices.
Implementation Method 1
addition of CoO having positive magnetic anisotropy is effective
Implementation Method 2
suppress exaggerated grain growth
Implementation Method 3
enhance domain wall motion
Data Source
AI summary
Disclosed is a MnZnCo-based ferrite consisting of base constituents, accessory constituents, and inevitable impurities, which MnZnCo-based ferrite is characterized by adding silicon oxide (SiO2 conversion): 50-400 mass ppm and calcium oxide (CaO conversion): 1000-4000 mass ppm as secondary constituents to base constituents consisting of iron oxide (Fe2O3 conversion): 51.0-53.0 mol %, zinc oxide (ZnO conversion): greater than 12.0 mol % and less than 18.0 mol %, cobalt oxide (CoO conversion): 0.04-0.60 mol %, and manganese oxide (MnO conversion): remainder, and keeping phosphorus, boron, sulfur, and chlorine of the inevitable impurities to phosphorous: less than 3 mass ppm, boron: less than 3 mass ppm, sulfur: less than 5 mass ppm, and chlorine: less than 10 mass ppm. This MnZnCo-based ferrite has the superior characteristics of always having incremental permeability [mu]? of 2000 or greater across a wide temperature range of −40 DEG C. to 85 DEG C. when a 33 A/m direct current magnetic field is applied, even in cases when formed into a small core with outside diameter of approximately 2-6 mm.