Bob Johnson Associates - Ceramic Magnets

Ceramic or Ferrite Magnets

The chemical composition of Ferrite magnets is SrO-6(Fe₂O₃), strontium hexaferrite. The raw materials used to produce ferrite magnets are strontium carbonate and iron oxide, both of which are readily available and low in cost. As a result, the use of ferrite magnets in most applications is more economical than other materials.

Sintered Ceramic/Ferrite magnets are formed by compaction in dedicated, multi-cavity dies followed by sintering in high temperature furnaces. This produces a hard, brittle part that requires specialized equipment for grinding to close tolerances. While physically quite strong, these magnets [like all cast or sintered magnetic materials] should not be considered a structural member in an assembly. And like most ceramics, they are brittle [not unlike glass] and should be handled with due care to avoid chipping and cracking.

The corrosion resistance of Ceramic/Ferrite is considered excellent, and no surface treatments are required. Ferrite magnets may have a thin film of fine magnet powder on the surface and for clean, non-contaminated applications some form of coating may be required. They are rather porous, and there may be applications were the surface should be sealed. Urethanes and epoxies work well. In addition, ferrite magnets lend themselves to printing.

Hard Ferrite magnets have excellent corrosion resistance and have normal operating capabilities between -40°C and +250°C. At very low temperatures there is a risk of permanent demagnetization in magnet systems with low permeance coefficients. Ferrite magnets have good intrinsic coercivity, making them resistant to demagnetizing effects.

DC permanent magnet motors, especially for the automotive industry [blowers, window lifts, windshield wiper motors, etc.].
Separators [removing ferrous materials from liquid, powder and bulk commodities].
Magnetic couplings.
Holding-magnet systems.
Sensor Applications.

Ceramic - Injection Molded

Ceramic - Sintered

Due to their low cost, Ferrite magnets enjoy a very wide range of applications:

Ceramic - Bonded