Sintered Ferrite Magnet: Composition, Properties, and Applications
A sintered ferrite magnet is one of the most widely used permanent magnets in modern industries. Known for its affordability, chemical stability, and strong resistance to demagnetization, it plays a crucial role in both consumer electronics and industrial machinery.
What Is a Sintered Ferrite Magnet?
A sintered ferrite magnet is a type of permanent magnet made by compacting and sintering a fine powder of iron oxide mixed with either barium or strontium carbonate. Through the sintering process—which involves heating the material below its melting point—the magnetic particles fuse together, forming a dense and durable magnetic structure.
These magnets are also known as ceramic magnets, and they are preferred for their balance between performance and cost.
Manufacturing Process
The production of sintered ferrite magnets involves several precise stages:
Raw Material Preparation – Iron oxide and strontium or barium carbonate are mixed in accurate proportions.
Calcination – The mixture is heated to create ferrite powder.
Milling – The calcined material is ground into a fine powder.
Pressing – The powder is pressed into molds using magnetic or non-magnetic fields.
Sintering – The pressed shapes are heated at around 1200°C to form solid magnets.
Machining and Finishing – The magnets are cut, polished, and coated (if required).
Key Properties
High Coercivity: Resistant to demagnetization, even under strong external magnetic fields.
Chemical Stability: Corrosion and oxidation-resistant without coating.
Temperature Resistance: Operates effectively between -40°C to 250°C.
Cost-Effective: Less expensive compared to rare-earth magnets.
Moderate Strength: Lower magnetic strength than NdFeB or SmCo magnets but sufficient for many uses.
Common Applications
Sintered ferrite magnets are used across numerous industries due to their reliability and stability. Major applications include:
Electric Motors and Generators
Loudspeakers and Audio Equipment
Magnetic Separators and Sensors
Refrigerator Door Seals
Magnetic Toys and Educational Tools
Automotive Components (e.g., wipers, window motors)
Advantages over Other Magnets
Compared to rare-earth magnets, sintered ferrite magnets are more environmentally friendly and economically viable. They perform well in harsh environments and do not require protective coatings, reducing maintenance costs. Their high electrical resistivity also minimizes eddy current losses, making them ideal for alternating magnetic field applications.
Conclusion
The sintered ferrite magnet remains a cornerstone in magnetic material technology, offering durability, stability, and affordability. Whether in everyday electronic gadgets or industrial machinery, its role is vital in driving efficient and sustainable magnetic performance.