ferrites and its application

a factual and brief description about ferrites, for more details refer to the references

1. FERRITES AND ITS APPLICATION SAP2109 (Condensed Matter P hysics) BY – ADITYA NARAYAN SINGH ROLL – IPH/10034/17 GUIDED BY – Dr S K ROUT DATE – 14 APRIL 2021 REFERENCE - PDF Name( Ferrites, Richaferrites, Catalytic activity of prepared…)

2. An Overview The history of ferrites (magnetic oxides) and their applications have been known for several centuries ago. The loadstone (magnetite, Fe3O4 ), a natural non-metallic solid, may attract iron was first described in known Greek writings about 800 B.C. Much later, the first application of magnetite was as 'Lodestones' used by early navigators to locate magnetic North. That is the first scientific significance was appreciated, after the first technical magnetic material because it formed the first compass ( Crangle , 1977). The first scientific study of magnetism named De Magnete was published by William Gilbert in 1600. Later, in 1819 Hans Christian Oersted observed that an electric current in a wire affected a magnetic compass needle. Naturally occurring magnetite is a weak 'hard' ferrite. 'Hard' ferrites possess a magnetism which is essentially permanent. Originally manufactured in a few select shapes and sizes, primarily for inductor and antenna applications, 'soft' ferrite has proliferated into countless sizes and shapes for a multitude of uses. Furthermore, ferrites are used predominately in three areas of electronics: low level applications, power applications, and Electro-Magnetic Interference (EMI) suppression . The breadth of application of ferrites in electronic circuitry continues to grow. The wide range of possible geometries, the continuing improvements in material characteristics and their relative cost-effectiveness make ferrite components the choice for both conventional and innovative applications.

3. Contd. Basically, ferrites are ceramic materials, dark grey or black in appearance and very hard and brittle. Ferrites may be defined as magnetic materials composed of oxides containing ferric ions as the main constituent (the word ferrite comes from the Latin “ ferrum ” for iron) and classified as magnetic materials because they exhibit ferrimagnetic behavior. The ferrites, in powder or thin film forms, can be prepared by high-temperature solid-state reaction method, sol–gel method, co precipitation , pulsed laser deposition, high-energy ball milling and hydrothermal technique. These are some ferrites structure :

4. CLASSIFICATION OF FERRITES The commercial ferrites, can be divided into three important classes, with each one having a specific crystal structure, namely: 1.Soft ferrite with the garnet structure such as the microwave ferrites e.g. YIG 2. Soft ferrites with the cubic spinel structure such as NiZn -, MnZn -, and MgMnZn ferrites 3. Hard ferrites with the magneto- plumbite (hexagonal) structure such as Ba and Sr hexa ferrites. Depending on crystal structure we have – 1- Spinel Ferrites 2- Garnet Ferrites 3- Ortho ferrites 4- Hexagonal Ferrites

5. According to nature of magnet On the basis of their magnetic properties that is temporary and permanent we classify ferrites in two part that is hard and soft. Hard ferrites : permanent ferrite magnets (or hard ferrites), which have a high remanence after magnetization, are composed of iron and barium or strontium oxides. These are the most commonly used magnets in radios. The maximum magnetic field B is about 0.35 Tesla and the magnetic field strength H is about 30 to 160 kA turns per meter ( 400 - 2,000 Oe ). Hard ferrites have a hexagonal structure and can be classified as M-, W-, X-, Y-, and Z-type ferrites . Soft ferrites : Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, or manganese compounds. They have a low co ercivity and are called soft ferrites. Due to their comparatively low losses at high frequencies, they are extensively used in the cores of switched-mode power supply (SMPS) and radio-frequency (RF) transformers and inductors.

6. Structure of ferrite material The crystal lattice of ferrite is spinel. Ferrites are a class of spinel material that adopt a crystal motif consisting of cubic close-packed (or face-centered cubic, FCC) oxides (O2−) with M cations occupying one eighth of the tetrahedral holes and M cations occupying half of the octahedral holes. The ferrite structure, whether it is garnet, spinel, or magnetoplumbite , has as its backbone a close-packed structure of oxygen anions. Metallic cations, magnetic and nonmagnetic, reside on the interstices of the close-packed oxygen lattice. Spinel ferrites may color less but are usually various shades of red, blue, green, yellow, and brown. The crystal lattice of ferrite is spinel. Metal ions are located at octahedral and tetrahedral positions. Fe2+, Ni2+, and Mn2+ ions prefer to occupy the octahedral sites and Fe3+ and Zn2+ ions prefer octahedral sites.

7. Synthesis techniques Synthesis techniques play an important role in controlling the size and surface area of materials. Different synthesis material yields different grains size and get operated t different temperatures as per the requirements .The synthesis of nanoparticles of magnetic materials (ferrites) has been reported using different chemical methods; that is, sol-gel, sono chemical , solvo thermal , precipitation, micro emulsion , etc. Further many characterization techniques like surface morphology and scanning electron microscope is used to study the products. Various methods are used for synthesis of spinel ferrites, which are listed below :- Sol – gel method (optics, electronics, space energy) Precipitation method Ball milling method ( cement, fireproof material, fertilizers) Solid state reaction method (mixing of grinded solid takes place)

8. Brief of different types Spinel : Ferrites with the formula AB2O4, constitute the first group of ferrites, where A and B represent various metal cations like iron. Spinel ferrites are magnetically soft and they are alternative to metallic magnets such as Fe and layered Fe-Si alloys, but exhibit enhanced performance due to their outstanding magnetic properties (Snelling 1969, Sugimoto 1999). Spinel ferrites have the properties such as high electrical resistivity and low magnetic loss. The two popular ceramic magnets; Nickel-Zinc ferrites and Manganese-Zinc ferrites are the major members of the spinel ferrite family. They have been intriguing ceramic materials due to their high electrical resistivity, 8 high magnetic permeability and possible modification of intrinsic properties over a wide spectrum (Hench and West 1990). Members of the spinel group include : Aluminium spinels - Chrysoberyl (BeAl2O4), Gahnite (ZnAl2O4) Iron spinels - Jacobsite (MnFe2O4), Magnesioferrite (MgFe2O4) Chromium spinels - Magnesiochromite (MgCr2O4), Zincochromite (ZnCr2O4) Other spinels - Coulsonite (FeV2O4 ), Magnesiocoulsonite (MgV2O4)

9. Garnet The chemical formula for ferrimagnetic garnet is Me3Fe5O12 where, Me is a trivalent ion such as rare earth or yttrium. The unit cell is cubic and contains eight molecules of Me3Fe5O12 i.e. (160 atoms). The metal ions are distributed over three types of sites. The Me ions occupy the dodecahedral sites (called c sites), where they are surrounded by eight oxygen ions, the Fe3+ ions distributed over the tetrahedral and octahedral sites in the ratio 3:2. Thus, the cation distribution of Me3Fe5O12 can be written as Me2Fe2Fe3O12. As in the case of spinels , the magnetic alignment results from super exchange interaction via the intervening oxygen ions, and the interaction is expected to be greater for the shorter the Me-O distance and closer the Me-O-Me angle is to 180 degree. On this basis it is concluded that the interaction between the Fe2 & Fe3 cations are relatively strong. Image shows garnet ferrite.

10. Ortho ferrites Ortho-ferrites have the general formula MeFeO3, where, Me is a large trivalent metal ion, such as rare-earth ion or Y. They crystallize in a distorted perovskite structure with an orthorhombic unit cell. These ortho-ferrites show a weak ferromagnetism, which has been attributed to the small canting in the alignment of two anti- ferromagnetically coupled lattices. The canting angle is of the order of 10-2 radian but is sufficient to introduce a small net ferromagnetic moment perpendicular to the antiferromagnetic axis. The direction of spin orientation of the Fe ion in HOFeO3 and ErFeO3 has been experimentally determined (9) at room temperature and found to be parallel to the (100) axis on lowering the temperature the spin axis rotates, and at 1.25 K the direction is ( 0 0 1 ) for HOFeO3 and ( 1 1 0 ) for ErFeO3. The spin moment on the rare earth ion gets ordered at a much lower Neel temperature [6.5 K for HO Fe O3 and 4.3 K for ErFeO3]. Image with ortho ferrite.

11. Hexagonal ferrites There are a number of ferrites that crystallize in hexagonal structure, and some of them have gained considerable technological importance in recent years. These ferrites are further sub-classified into M, W, Y, Z and U compounds. All these have different, though related, crystal structures. The M compounds have the simplest structure. Barium ferrite, the well known hard ferrites, belongs to this class. These compounds have the general formula MeFe12O19 where Me is a divalent ion of a large ionic radius, such as Ba2+, Sr2+, or Pb2+. Some compounds with trivalent Me (e.g. La3+, Al, Ga, Cr, Fe) are also known. In these, one iron per formula unit is present as Fe2+ to allow for the charge compensation. The crystal structure of barium ferrite is hexagonal with the unit cell made up of two unit formulae. The structure is related to the spinel structure in which the oxygen lattice, f.c.c ., consist of a series of hexagonal layers of oxygen lying perpendicular to the (111) direction . Image of hexa-ferrite.

12. Advantages of ferrites Ferrites have a paramount advantage over other types of magnetic materials, some of those are listed below : 1. Low eddy current loss 2. high permeability 3. High resistivity 4. Wide frequency range (10 kHz to 50 MHz) 5. Low cost 6. Large selection material 7. Shape versatility 8. Economical assembly 9. Temperature and time stability 10. High Q/small package

13. Application of Ferrites Ferrites are regarded as better magnetic materials than pure metals because of their high resistivity, lower cost, easier manufacture and superior magnetization properties. Ferrites are extensively used in radar, audio–video and digital recording, bubble devices, memory cores of computers, satellite communication and microwave devices [1-3]. Ferrite has a vast application from microwave to radio frequencies. It is used for antenna cores in radio receivers, fly back transformer in TV picture tube, broad band transformer, mechanical filter, ultrasonic generator, moderators, phase shift, isolators. Here are some other fields where we use ferrites extensively High-Density Write-Once Optical Recording - Thin films of defect spinel ferrites can be used as write-once read many media working with blue wavelengths. Magnetic sensors - These are used for temperature control and these can be made using ferrite with sharp and definite Curie temperature . Magnetic Shielding - A radar absorbing paint containing ferrite has been developed to render an aircraft of submarine invisible to radar.

14. Some more applications Pollution Control - There are several Japanese installations which use precipitation of ferrite precursors to scavenge pollutant materials such as mercury from waste streams . Ferrite electrodes - Because of their high corrosion resistance, ferrites having the appropriate conductivities have been used as electrode in applications such as chromium plating . Entertainment ferrites - Ferrites are widely used in radio and television circuits. Typically applications include deflection Yokes, fly back transformers and SMPS transformer for power applications. Some other applications are listed below: Power transformer and chokes: HF Power supplies and lighting ballasts Inductors and tuned transformers: Frequency selective circuits Pulse and wideband transformers: Matching devices Magnetic deflection structures: TV sets and monitors Recording heads: Storage devices Rotating transformers: VCR’s

15. Some more applications Shield beads and chokes: Interference suppression Transducers: Vending machines and ultrasonic cleaners Catalysis: high surface area, controlled crystal surfaces Optical properties: sun screen, hyper thermic cancer treatment, fluorescent tags Light scattering: smoke/fog screens Drug delivery: inhalation asthma, timed drug release Pesticide delivery: fogging and fumigation Magnetic recording: orient magnetic domain axis, important for hard drives, video & audio tapes Pigments, inks, paints: colouring and opacity

16. Future of ferrites Ferrites are mistakenly believed to be fully developed in all fields of science, technology, and application. Ferrite material are recognized as more important and essential for the further development of electronics than before, and it is believed that the production of ferrites will increase year by year as their applications become more diverse. Reviewing ferrite history and accurately analyzing its present situation will add greatly to further development in the future. Magnetic ferrite nanoparticles are being applied in diversified areas of technology because of their unique magnetic, chemical, and structural properties. The recent advances in the architecture design of multifunctional magnetic nano ferrites with fine-tuned properties boosted the birth of innovative applications.

17. That was all from my side