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Application of electroceramics

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  • 1. Application ofApplication ofElectroceramicsElectroceramics
  • 2. Capacitors The multilayer ceramic (MLC) capacitors. The MLCC structure consists of alternate layers ofdielectric and electrode material. Each individual dielectric layer contributescapacitance to the MLCC as the electrodesterminate in a parallel configuration. The advances in preparation technology havemade it possible to make dielectric layers <1 µmthick.
  • 3. Schematic of a typical multilayerceramic (MLC) capacitorCut-away view of multilayerceramic capacitor.
  • 4. Applications of Ferroelectric ThinFilms Ferroelectric thin films have attracted attention forapplications in many electronic and electro-opticdevices. Applications of ferroelectric thin films utilize theunique dielectric, piezoelectric, pyroelectric, andelectro-optic properties of ferroelectric materials. Some of the most important electronic applications offerroelectric thin films include nonvolatile memories,thin films capacitors, pyroelectric sensors, andsurface acoustic wave (SAW) substrates. The electro-optic devices include optical waveguidesand optical memories and displays.
  • 5.  Semiconductor memories such as DRAM & SRAMcurrently dominate the market. However, the disadvantage of these memories is thatthey are volatile, i.e. the stored information is lost whenthe power fails. The non-volatile memories available at this time includecomplementary metal oxide semiconductors (CMOS)with battery backup and electrically erasable read onlymemories (EEPROMs). These non-volatile memories are very expensive.Ferroelectric Memories
  • 6. FeRAM Cross Section
  • 7. FeRAM FeRAM is a type of nonvolatile RAM that uses aferroelectric film as a capacitor for storing data. FeRAM can achieve high-speed read/writeoperations comparable to that of DRAM, withoutlosing data when the power is turned off (unlikeDRAM). In addition to nonvolatility and high-speed operation,FeRAM cells offer the advantages of easyembedding into VLSI logic circuits and low powerconsumption, perhaps their greatest advantage formany applications.
  • 8.  FeRAM-embedded VLSI circuits have beenused in smart cards, radio frequency identification (RFID) tags, and as a replacement for BBSRAM (batterybacked-up static RAM), which is used in variousdevices to protect data from an unexpectedpower failure, as well as in many other SoC(system on a chip) applications.FeRAM
  • 9.  A memory cell, where one bit of data is stored, iscomposed of a cell-selection transistor and a capacitorfor 1T1C (one transistor, one capacitor)-type FeRAM. A major problem encountered when reducing the size ofthe memory cell is preventing reliability degradation. The reliability of FeRAM cells is dependent on the materials used (ferroelectric film, electrode, interlayerdielectric, etc.), fabrication process, device structure, memory cell circuit, and operation sequence.FeRAM
  • 10. Schematic drawings of field-effect transistors (FETs) with(a) metal–ferroelectric–insulator–semiconductor (MFIS) and(b) metal–ferroelectric–metal–insulator–semiconductor (MFMIS)gate structures.
  • 11. MFIS structures The MFIS structure is simple and small in area. Thus, it is suitable for high-density integration. In an MFIS structure, the effect of the leakagecurrent is localized around weak spots in the film;this is important in prolonging the data retentiontime. In other words, in an MFIS structure, the effect ofthe leakage current spreads out to the whole floatinggate, and the charge neutrality is completelydestroyed in a short time. Thus, an MFIS structure issuperior in this regard.
  • 12. MFMIS structures In an MFMIS structure, it is possible to optimize thearea ratio between the ferroelectric and buffer layercapacitors, so that the induced charges on bothcapacitors match. In an MFMIS structure, the floating gate materialcan be so chosen that a highquality ferroelectric filmis formed on the floating gate and that constituentelements in the ferroelectric film do not diffuse intothe buffer layer and Si substrate.
  • 13. Electro-optic Applications The requirements for using ferroelectricthin films for electro-optic applicationsinclude an optically transparent film with ahigh degree of crystallinity. The electro-optic thin film devices are oftwo types; one in which the propagation oflight is along the plane of the film (opticalwaveguides) and the other in which thelight passes through the film (opticalmemory and displays).
  • 14. Other Ferroelectric Thin FilmApplicationsThin Film Capacitors: The high dielectric permittivity of ferroelectricceramics such as BaTiO3, PMN and PZT very usefulfor capacitor applications. The MLC capacitors have a very high volumetricefficiency (capacitance per unit volume) becauseof the combined capacitance of thin ceramic tapes(~ 10-20 m m) stacked one on top of the other.
  • 15. Pyroelectric Detectors : Pyroelectricity is the polarization produced due toa small change in temperature. Single crystals of triglycine sulfate (TGS), LiTaO3,and (Sr,Ba)Nb2O6are widely used for heat sensingapplications. PbTiO3, (Pb,La)TiO3and PZT have been widelystudied for thin film pyroelectric sensingapplications.
  • 16. Surface Acoustic Wave Substrates : SAW devices are fabricated by depositinginterdigital electrodes on the surface of apiezoelectric substrate. An elastic wave generated at the input interdigitaltransducer (IDT) travels along the surface of thepiezoelectric substrate and it is detected by theoutput interdigital transducer. These devices are mainly used for delay lines andfilters in television and microwavecommunication applications.
  • 17. Schematic representation of the generation,propagation and detection of surface acousticwaves (SAW) on a piezoelectric substrate withinterdigital electrode.
  • 18. Gas Ignitors  It consists of two oppositelypoled ceramic cylindersattached end to end in order todouble the charge available forthe spark. The compressive force has tobe applied quickly to avoid theleakage of charge across thesurfaces of the piezoelectricceramic. The generation of the sparktakes place in two stages. Theapplication of a compressiveforce F on the poled ceramic(under open circuit conditions)leads to a decrease in thelength by dLD. The potential energy developedacross the ends must be higherthan the breakdown voltage ofthe gap, for sparking to occur.A piezoelectric spark generator
  • 19. Gas Ignitors  When the spark gap breakdownoccurs the second stage ofenergy generation starts. The electric discharge across thegap results in a change fromopen circuit conditions to closedcircuit conditions with the voltagedropping to a lower level. The combination of the strainsfrom the open and short circuitconditions produce more energythat can be dissipated in thespark. Usually PZT ceramic disks areused for this application.A piezoelectric spark generator
  • 20. Actuators & SensorsSchematic description of the geometry and the working principleof the piezoelectric film applied in actuators and sensors.
  • 21. Actuators & Sensors An important family of functional materialsare ferroelectrics or, more generally, polarmaterials. Their piezoelectricity can be used in sensors,actuators, and transducers; Their pyroelectricity is employed in infrareddetectors.
  • 22. Piezoelectric Microactuator DevicesSchematic draw of optical scanning device withdouble layered PZT layer (a) and thefabricated device, (b) Mirror plate: 300×300(µm2, DPZT beam: 800 × 230 µm2).Schematic drawing of self-actuationcantilever with an integratedpiezoresistor.Micropump using screen-printed PZTactuator on silicon membrane.(Courtesy of Neil White, Univ. ofSouthampton, UK.)
  • 23. Aplication of Magnetic Ceramics Entertainment electronic (Radio, TV) Computer Microwave applications (Radar,communication, heating) Recording Tape Permanent motor
  • 24. Aplication of Magnetic Ceramics Spinel (cubic ferrites): Soft magnets Garnet (rare earth ferrites): Microwave devices Magnetoplumbite (hexagonal ferrites): Hardmagnets
  • 25. Aplication of Soft Magnetics In the soft magnetic materials, only a small field isnecessary to cause demagnetization and very smallenergy losses occur per cycle of hysteresis loop. This is important for applications such astransformers used in touch tone telephones orinductors or magnetic memory cores. During used a soft ferrites has its magnetic domainsrapidly and easily realigned by the changingmagnetic field.
  • 26. Aplication of Hard Magnetics A hard (or permanent) ceramic magnet achieves itsmagnetization during manufacture. The magnetic domains are “frozen in” by poling inan applied magnetic field as the material is cooledthrough its Tc. The materials are magnetically very hard and willretain in service the residual flux density, thatremains after the strong magnetizing field has beenremoved. Hard ferrites are used in loudspeakers, motors.
  • 27. Aplication of Ferrites The cubic spinels, also called ferrospinels, areused as soft magnetic materials because of theirvery low coercive force of 4x10-5weber/m2and highsaturation magnetization 0.3-0.4 weber/m2.(1 weber = 1 volt-second = 108Maxwells) Flux density (induction): 1 Tesla = 104Gauss = 1weber/m2. (1 Gauss = 1 Maxwell/cm2). Hexagonal ferrites are hard magnetic materials withcoercive force of 0.2 – 0.4 weber/m2and largeresistance to demagnetization, 2 – 3 J/m3.
  • 28. Aplication of Garnets Garnets are especially suited for high frequencymicrowave applications due to the ability to tailorproperties such as magnetization, line width, g-factor, Tc, and temperature stability. The most common garnet ferrites are based upon3Y2O3: 5Fe2O3or Y3Fe5O12or YIG.
  • 29. Tape Recording Before passing over the record head,a tape passes over the erase headwhich applies a high amplitude, highfrequency magnetic field to the tapeto erase any previously recordedsignal and to thoroughly randomizethe magnetization of the magneticemulsion. The gap in the erase head is widerthan those in the record head; thetape stays in the field of the headlonger to thoroughly erase anypreviously recorded signal.
  • 30. Tape Recording High fidelity tape recording requires a high frequencybiasing signal to be applied to the tape head along withthe signal to "stir" the magnetization of the tape . This is because magnetic tapes are very sensitive to theirprevious magnetic history, a property called hysteresis. A magnetic "image" of a sound signal can be stored ontape in the form of magnetized iron oxide or chromiumdioxide granules in a magnetic emulsion. The tiny granules are fixed on a polyester film base, butthe direction and extent of their magnetization can bechanged to record an input signal from a tape head.
  • 31. Electromagnet Electromagnets are usually in the form of iron coresolenoids. The ferromagnetic property of the iron core causesthe internal magnetic domains of the iron to line upwith the smaller driving magnetiv field drivingproduced by the current in the solenoid. The solenoid field relationship isand k is the relative permeability of the iron, showsthe magnifying effect of the iron core.
  • 32. Transformer A transformer makes use of Faraday’s law and theferromagnetic properties of an iron core to efficientlyraise or lower AC voltages. It of course cannot increase power so that if the voltageis raised, the current is proportionally lowered and viceversa.
  • 33. Transformer
  • 34. Applications of GMR The largest technological application of GMR is in the datastorage industry. IBM were first to market with hard disks based on GMRtechnology although today all disk drives make use of thistechnology. On-chip GMR sensors are available commercially fromNon-Volatile Electronics. It is expected that the GMR effect will allow disk drivemanufacturers to continue increasing density at least untildisk capacity reaches 10 Gb per square inch. At this density, 120 billion bits could be stored on a typical3.5-inch disk drive, or the equivalent of about a thousand30-volume encyclopedias.
  • 35. Applications of GMR Other applications are as diverse as solid-statecompasses, automotive sensors, non-volatilemagnetic memory and the detection of landmines.
  • 36. Applications of GMR GMR also may spur the replacement of RAM incomputers with magnetic RAM (MRAM). Using GMR, it may be possible to make thin-filmMRAM that would be just as fast, dense, andinexpensive. It would have the additional advantages of beingnonvolatile and radiation-resistant. Data would not be lost if the power failed unexpectedly,and the device would continue to function in thepresence of ionizing radiation, making it useful forspace and defense applications.
  • 37. Applications of GMR Reading and writing with a magnetoresistive probe. C B Craus, T Onoue, K Ramstock,W G M A Geerts, M H Siekman, L Abelmannand J C Lodder, J. Phys. D: Appl. Phys. 38 (2005) 363–370
  • 38. Application of SuperconductorsPower lines. A significant amount of electrical energy is wasted as heatwhen electricity is transmitted down cables made of traditionalmetal conductors. Superconductors, can conduct electricity with zero resistanceand would therefore be more efficient.Transport. Magnetically levitated trains already exist. Using superconducting magnets, cheaper, faster and moreefficient variants could be produced.Electronics. By harnessing the Josephson effect, extremely fast electronicswitches could be constructed, allowing faster microprocessorsto be built.
  • 39. Microwave DielectricsMicrowave Dielectrics The Microwave materials including of dielectric andcoaxial resonators to meet the demands of microwaveapplications for high performance, low cost devices insmall, medium and large quantities. Applications Patch antennas Resonators /inductors Substrates C-band resonator-mobile Filters
  • 40. Dielectric Resonator (DR) Used in shielded microwave circuits,such as cavity resonator, filters andoscillators. Application: as antenna in microwaveand millimeter band. Advantages of DR: light weight, low cost, small size, highradiation efficiency, large bandwidth.
  • 41. High-K dielectric to reduce size Dielectric Resonator (DR)size is inversely proportionalto the frequency: Larger ε, lower frequency Larger ε, smaller sizeεLcf2=
  • 42.  Photograph of split post dielectric resonatorsoperating at frequencies: 1.4, 3.2 and 33 GHz.Jerzy Krupka, Journal of the European Ceramic Society 23 (2003) 2607–2610
  • 43. Super-K CCTOSuper-K CCTO