Li-based Ferrite Material with Bi2O3 for High Permeability
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Solution Overview
Problem
Conventional Li-based ferrite materials struggle to achieve high initial permeability, high saturation magnetic flux density, and high resistivity simultaneously, especially at high temperatures, while also being cost-effective and resistant to stress, which is essential for applications like inductors and antennas.
Innovation Solution
A sintered ferrite material with a composition formula of (1-x-y-z)(Li0.5Fe0.5)O·xZnO·yFe2O3·zCuO, where x, y, and z are within specific ranges, is produced through pre-sintering, adding Bi2O3, pulverizing, and sintering at controlled temperatures, eliminating the need for complex heat treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a Li-based ferrite material is sintered at a high temperature equal to or higher than 1000°C, then the material can be processed effectively, but it is difficult to obtain high resistivity (equal to or higher than 10^6 Ωm)
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sintering temperature range (1000-1200°C) and duration (2-5 hours) to achieve optimal resistivity. Additionally, the composition parameters are optimized with specific ratios of Li2O (10-20 mol%), ZnO (3.5-20 mol%), Fe2O3 (70-85 mol%), and Bi2O3 (2-30 mass%), which together resolve the contradiction between high-temperature processing and high resistivity requirements.
2Quantity of substance
If a Li-based ferrite material is used to enhance saturation magnetic flux density, then the material can be used in inductors and antennas, but the saturation magnetic flux density is lower than that of Ni-based ferrite material
Solution Approach 1:
The patent uses composite materials by combining Li2O, ZnO, Fe2O3, and Bi2O3 in specific proportions to create a Li-based ferrite composite material. This composite approach enhances the saturation magnetic flux density to 430 mT or more at 23°C and 380 mT or more at 100°C, making it comparable to Ni-based ferrite materials while avoiding the use of expensive nickel.
3Object-affected harmful factors
If complex heat treatments are applied to enhance resistivity, then the material properties can be improved, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent applies preliminary action by incorporating Bi2O3 (2-30 mass%) into the base composition before sintering. This pre-addition of Bi2O3 provides inherent resistivity enhancement that maintains high resistivity (10^6 Ωm or more) after sintering at 1000-1200°C, eliminating the need for subsequent complex heat treatments in nitrogen and oxygen atmospheres.
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 method results in a sintered ferrite material with initial permeability of 200 or higher, saturation magnetic flux density of 430 mT or more at 23°C and 380 mT or more at 100°C, and resistivity of 10^6 Ωm or higher, reducing manufacturing costs and stress sensitivity, suitable for various core materials.
Implementation Method 1
a first pre-sintering step of pre-sintering the mixed raw materials; a second sintering step of sintering the compact at a sintering temperature of 1000°C to 1200°C
Data Source
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AI summary
A sintered ferrite material, which is obtained by adding Bi2O3 in a range from 0.5 % by mass to 3 % by mass against 100 % by mass of a material having a composition formula of (1-x-y-z)(Li0.5Fe0.5)O·xZnO·yFe2O3·zCuO wherein x, y and z satisfy 0.14≤x≤0.19, 0.48≤y<0.5 and 0≤z≤0.03 and satisfies resistivity equal to or higher than 106 Ωm, initial permeability equal to or higher than 200 and saturation magnetic flux density equal to or higher than 430 mT at 23 °C and equal to or higher than 380 mT at 100 °C.