What are sintered ferrite magnets?

Sintered ferrite magnets, also known as ceramic magnets, are one of the most widely used permanent magnetic materials in the world. Thanks to their stable performance, cost efficiency, and resistance to corrosion, sintered ferrite magnets play an essential role in many everyday and industrial applications.

Definition of Sintered Ferrite Magnets

Sintered ferrite magnets are permanent magnets made primarily from iron oxide (Fe₂O₃) combined with either barium carbonate or strontium carbonate. These raw materials are processed through a high-temperature sintering method, which gives the magnets their solid structure and magnetic characteristics.

Compared with rare-earth magnets, sintered ferrite magnets offer moderate magnetic strength but excellent chemical stability and affordability, making them ideal for mass-market products.

How Are Sintered Ferrite Magnets Manufactured?

The production of sintered ferrite magnets involves several precise steps:

Raw Material Preparation

Iron oxide is mixed with barium or strontium compounds in carefully controlled proportions.

Calcination

The mixture is heated at high temperatures to form ferrite powder with magnetic properties.

Molding and Pressing

The powder is pressed into specific shapes, either with or without an external magnetic field to control magnetic orientation.

Sintering

The pressed parts are fired at temperatures above 1,200°C, allowing particles to bond and densify.

Grinding and Finishing

Final machining ensures accurate dimensions and surface quality.

This sintering process is what gives sintered ferrite magnets their name and their durable, ceramic-like structure.

Key Properties of Sintered Ferrite Magnets

Sintered ferrite magnets have several important characteristics that make them suitable for a wide range of applications:

Good Magnetic Stability

They maintain stable magnetic performance under normal operating conditions.

Excellent Corrosion Resistance

Unlike many metal magnets, sintered ferrite magnets do not require protective coatings.

High Electrical Resistivity

This reduces eddy current losses, especially in motor applications.

Cost-Effective

Their raw materials are abundant, making them significantly cheaper than rare-earth magnets.

However, it is important to note that sintered ferrite magnets are relatively brittle and have lower magnetic energy compared to NdFeB magnets.

Common Applications of Sintered Ferrite Magnets

Due to their balanced performance and low cost, sintered ferrite magnets are used in many industries, including:

Electric motors and generators

Loudspeakers and audio equipment

Household appliances

Automotive components

Magnetic separators

Educational and consumer products

Their reliability and long service life make sintered ferrite magnets especially attractive for high-volume production.

Advantages and Limitations

Advantages

Low manufacturing cost

Strong resistance to rust and chemicals

Stable performance over time

Suitable for large-scale applications

Limitations

Lower magnetic strength than rare-earth magnets

Brittle material, not suitable for impact-heavy environments

Limited design flexibility compared to bonded magnets

Understanding these advantages and limitations helps engineers choose the right magnet for specific applications.

Conclusion

Sintered ferrite magnets remain a cornerstone of the global magnet industry. With their simple composition, reliable performance, and cost efficiency, they continue to be widely used across electronics, automotive, and industrial sectors.

As demand for durable and economical magnetic solutions grows, sintered ferrite magnets will continue to play a vital role in modern technology and manufacturing.