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FERRITES

What is ferrite ? 

Ferrite is also known as ferrate

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Ferrites are explained as any of a group of nonmetallic, ceramic-like, usually ferromagnetic compounds of ferric oxide with other oxides, especially a compound characterized by extremely high electrical resistivity.

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Ferrites are composed of iron oxide and one or more other metals in chemical combination

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A ferrite is usually described by the formula M(FexOy), where M represents any metal(Mn,Co,Ni,Cu,Mg,Z,Cd or Fe++) that forms divalent bonds, such as nickel ferrite (NiFe2O4).

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Magnetic susceptibility is large, and the B-H characteristic shows the hysterisis effect common to the metallic ferromagnetics.

Ferrite may refer to…… 

Ferrite (iron) - iron or iron alloys with a body-centered cubic crystal structure

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Ferrite (magnet) - ferromagnetic ceramic materials used in magnetic applications

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Ferrite bead - components placed on the end of data cables to reduce interference

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Calcium aluminoferrite - a mineral found in cements

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Ferrite core - a structure on which the windings of electric transformers and other wound components are formed

Properties of Ferrites 

Hard

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Brittle

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Iron-containing

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Polycrystalline

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High electrical resistivity

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Low electrical losses

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Significant saturation magnetization

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Very good chemical stability

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Generally gray or black

Classification of Ferrites…..

Soft ferrites

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Soft ferrite does not retain significant magnetization.

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They have a low coercivity (manganese-zinc ferrite, nickel-zinc ferrite).

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Used in transformer or electromagnetic cores.

Hard Ferrites 

In hard ferrite magnetization is considered permanent.

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Have a high coercivity.

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They are cheap, and are widely used in household products such as refrigerator magnets (strontium ferrite, barium ferrite).

Characteristics…..

Applications……

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Ferrites have importance in engineering and technology because they possess spontaneous magnetic moment below the Curie temperature just as iron, cobalt, nickel.

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Due to vey low eddy current losses, ferrites are used as a core of coils in microwave frequency(high frequency) devices and computer memory core elements.

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Due to relatively low permeability and flux density compared to iron, ferrites are not suitable for the use in high field and high power applications, such as motors, generators and power transformers, but they can be used in low field and low power applications.

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Ferrites are used as ferromagnetic insulators in electrical circuits.

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Ferrites like ZnO find low frequency applications in timers. They are also used as switches in refrigerators, air conditioners, etc.

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Ferrites are used as magnetic head transducer in recording.

Some of the recent applications of ferrites are listed below 

Power transformer and chokes: HF Power supplies and lighting balasts

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Inductors and tuned transformers: Frequency selective circuits

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Pulse and wideband transformers: Matching devices

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Magnetic deflection structures: TV sets and monitors

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Recording heads: Storage devices

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Rotating transformers: VCR’s

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Shield beads and chokes: Interference suppresion

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Transducers: Vending machines and ultrasonic cleaners

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Catalysis: high surface area, controlled crystal surfaces

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Optical properties: sun screen, hyperthermic cancer treatment,

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fluorescent tags Light scattering: smoke/fog screens