Ferrite Magnetic Material Grades and Parameters

Soft Ferrite Grades and Parameters

Manganese - Zinc (Mn - Zn) Ferrites

• Grades: There are several grades of Mn - Zn ferrites, such as T38, T44, and T63. Each grade is designed to meet specific performance requirements in different applications. For example, T38 is often used in power transformers operating at relatively low frequencies (50 - 60 Hz) due to its high permeability and low core loss at these frequencies. T44 is suitable for medium - frequency applications like switching - mode power supplies, while T63 is used in high - frequency applications up to a few megahertz, such as in some types of inductors.
• Parameters
  • Permeability (μ): Mn - Zn ferrites have high initial permeabilities, typically ranging from 1000 to 10000. High permeability allows for efficient magnetic coupling and energy transfer in transformers and inductors. For instance, in a power transformer, a high - permeability core reduces the magnetizing current required, improving the overall efficiency of the transformer.
  • Core Loss (P): Core loss is a crucial parameter, especially in power - handling applications. It consists of hysteresis loss and eddy - current loss. Mn - Zn ferrites are designed to minimize core loss at their intended operating frequencies. At low frequencies, hysteresis loss dominates, while at high frequencies, eddy - current loss becomes more significant. By optimizing the composition and microstructure, manufacturers can reduce both types of losses.
  • Saturation Flux Density (Bs): The saturation flux density of Mn - Zn ferrites is relatively low, usually around 0.3 - 0.5 T. This limits the maximum magnetic flux that can be carried by the core without entering saturation. However, in many applications where high - flux operation is not required, such as in signal - processing transformers, this is not a major drawback.

Nickel - Zinc (Ni - Zn) Ferrites

• Grades: Common grades include N47, N72, and N97. N47 is often used in broadband transformers and EMI (Electromagnetic Interference) filters operating in the frequency range of 1 - 100 MHz. N72 is suitable for higher - frequency applications up to several hundred megahertz, such as in antenna cores for mobile communication devices. N97 is used in ultra - high - frequency applications, like in some types of microwave components.
• Parameters
  • Permeability (μ): Ni - Zn ferrites have lower permeabilities compared to Mn - Zn ferrites, typically in the range of 10 - 1000. This lower permeability is compensated by their ability to operate at much higher frequencies.
  • Resistivity (ρ): One of the key advantages of Ni - Zn ferrites is their high electrical resistivity, which can be as high as 10⁸ - 10¹⁰ Ω·m. High resistivity reduces eddy - current losses at high frequencies, making them ideal for high - frequency applications.
  • Curie Temperature (Tc): The Curie temperature of Ni - Zn ferrites is relatively high, usually above 200°C. This indicates that they can maintain their magnetic properties over a wide temperature range, which is important in applications where the device may be exposed to varying temperatures.

Hard Ferrite Grades and Parameters

Strontium Ferrite (SrFe₁₂O₁₉)

• Grades: Grades are often classified based on their magnetic properties, such as high - energy product (BH)max grades. For example, there are standard - performance grades with a (BH)max of around 28 - 32 kJ/m³ and high - performance grades with a (BH)max of up to 40 kJ/m³. High - performance grades are used in applications where a strong and stable magnetic field is required, such as in high - end loudspeakers and electric motors.
• Parameters
  • Remanence (Br): Strontium ferrites have a relatively high remanence, typically in the range of 0.35 - 0.45 T. Remanence is the magnetic flux density remaining in the material after the external magnetic field is removed, and a high value indicates that the magnet can retain a strong magnetic field.
  • Coercivity (Hc): The coercivity of strontium ferrites is high, usually around 200 - 400 kA/m. High coercivity means that the magnet is resistant to demagnetization, which is essential for permanent - magnet applications.
  • Temperature Stability: Strontium ferrites have good temperature stability. Their magnetic properties change relatively little over a wide temperature range, typically from - 40°C to 150°C. This makes them suitable for use in outdoor and automotive applications where temperature variations are common.

Barium Ferrite (BaFe₁₂O₁₉)

• Grades: Similar to strontium ferrites, barium ferrites are also graded based on their magnetic properties. There are general - purpose grades and high - performance grades. High - performance grades are used in applications where high magnetic strength and stability are required, such as in magnetic recording media and high - precision sensors.
• Parameters
  • Remanence (Br): Barium ferrites have a remanence in the range of 0.3 - 0.4 T, which is comparable to that of strontium ferrites.
  • Coercivity (Hc): The coercivity of barium ferrites is also high, around 150 - 350 kA/m. This high coercivity ensures that the magnet can withstand external magnetic fields and mechanical stresses without losing its magnetization.
  • Corrosion Resistance: Barium ferrites have excellent corrosion resistance. They are less likely to react with moisture and other environmental factors compared to some other magnetic materials, making them suitable for use in harsh environments.

Conclusion

The grades and parameters of ferrite magnetic materials play a crucial role in determining their suitability for various applications. Soft ferrites, with their high permeability and low core loss at specific frequencies, are ideal for transformers and inductors. Hard ferrites, on the other hand, with their high remanence and coercivity, are used as permanent magnets in a wide range of devices. Understanding these grades and parameters allows engineers and designers to select the most appropriate ferrite magnetic material for their specific needs, ensuring optimal performance and reliability of the final product.