MnZnCo Ferrite Composition Using Potassium for Stable Low Magnetic Loss
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Solution Overview
Problem
Conventional MnZnCo-based ferrite technologies struggle to achieve low magnetic losses over a wide frequency range and temperature range, particularly in automotive DC-DC converters, due to unstable thermal behavior and insufficient reduction in magnetic losses.
Innovation Solution
The addition of potassium (K) to the raw materials of MnZnCo-based ferrite, resulting in a sintered ferrite with specific compositions and grain size distributions, effectively reduces magnetic losses by enhancing specific resistivity and refining crystal grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional MnZnCo-based ferrite compositions are used, then the material can be manufactured with standard processes, but magnetic losses remain high and unstable over wide temperature and frequency ranges
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional ratios of Fe2O3 (51-58 mol%), ZnO (6-13 mol%), MnO (balance), and CoO (0.1-0.5 mol%), along with specific auxiliary components (SiO2: 50-500 mass ppm, CaO: 200-2000 mass ppm, Nb2O5: 85-500 mass ppm, K2O: 5-20 mass ppm). These compositional parameter adjustments optimize the magnetic anisotropy constant K1 to remain near zero across wide temperature ranges, thereby stabilizing magnetic losses while reducing overall energy loss in the 100 kHz to 500 kHz frequency range.
2Reliability
If Co2+ is added to reduce temperature dependence of K1, then magnetic loss stability over temperature improves, but magnetic loss reduction becomes insufficient at high frequencies
Solution Approach 1:
The patent employs composite material principles by combining MnZnCo-based ferrite with multiple auxiliary components (SiO2, CaO, Nb2O5, K2O) in specific proportions. This composite approach creates a multi-functional material system where CoO provides temperature stability of K1, while the auxiliary components collectively reduce magnetic losses at high frequencies through grain boundary effects and crystal grain refinement, achieving both stability and low loss performance simultaneously.
3Loss of energy
If auxiliary components are added to increase specific resistivity, then eddy current loss reduces, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the concentrations of auxiliary components within specific ranges (SiO2: 50-500 mass ppm, CaO: 200-2000 mass ppm, Nb2O5: 85-500 mass ppm, K2O: 5-20 mass ppm). These controlled parameter adjustments achieve effective eddy current loss reduction through increased specific resistivity while maintaining manageable manufacturing complexity, as the additives can be incorporated using conventional mixing and sintering processes without requiring complex manufacturing steps.
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
This approach enables MnZnCo-based ferrite to exhibit low magnetic losses of 360 kW/m3 or less at 100 kHz and 200 kW/m3 or less at 500 kHz, across a wide temperature range, thereby meeting the demands for efficient operation in automotive DC-DC converters.
Implementation Method 1
The magnetic anisotropy constant K1. Magnetic loss takes its minimum value at the temperature where K1=0. The closer the absolute value of K1 is to zero, the smaller the value of magnetic loss. The overall K1 of ferrite is determined by adding up the K1 of each of the elemental ions of the main components of ferrite. Fe2+ and Co2+ have positive K1, while Fe3+ and Mn2+ have negative K1. In addition, Co2+ can reduce the temperature dependence of K1, and thus the thermal variation of K1.
Implementation Method 2
it is effective to add substances other than the basic components that form high-resistivity phases at grain boundaries. For example, JP S36-002283 B(PTL 2) describes a technology in which oxides such as calcium oxide and silicon oxide are added in small amounts to MnZn ferrite as auxiliary components and caused to segregate at grain boundaries to increase the grain boundary resistance so that the overall resistivity is increased from about 0.01Ω·m to 0.05Ω·m to several Ω·m or more, thereby reducing eddy current losses
Implementation Method 3
Magnetic losses are classified into three types: hysteresis loss, eddy current loss, and residual loss. Among these, it is known that eddy current loss can be reduced by improving the specific resistivity of ferrite cores.
Implementation Method 4
Another technique to reduce magnetic losses in MnZnCo—based ferrite is the addition of K. The addition of K enables the segregation of auxiliary components at grain boundaries. This effect can reduce magnetic losses. Furthermore, K has the effect of refining crystal grains. Crystal grain refinement is effective in reducing magnetic losses, especially at high frequencies.
Implementation Method 5
MnZnCo—based ferrite consisting of basic components, auxiliary components, and inevitable impurities, wherein the basic components are Fe2O3: 51.00 mol % or more and less than 58.00 mol %, ZnO: 6.00 mol % or more and less than 13.00 mol %, and CoO: more than 0.10 mol % and 0.50 mol % or less, with the balance being MnO
Data Source
AI summary
To provide MnZnCo—based ferrite with small magnetic losses over a wide frequency range and a wide temperature range. Disclosed is MnZnCo—based ferrite containing basic components and auxiliary components, in which the basic components are Fe2O3: 51.00 mol % or more and less than 58.00 mol %, ZnO:6.00 mol % or more and less than 13.00 mol %, and CoO:more than 0.10 mol % and 0.50 mol % or less, with the balance being MnO, and the auxiliary components are 50 mass ppm to 500 mass ppm of Si in terms of SiO2, 200 mass ppm to 2000 mass ppm of Ca in terms of CaO, 85 mass ppm to 500 mass ppm of Nb in terms of Nb2O5, and 5 mass ppm to 20 mass ppm of K, relative to the basic components.