Application of Electroceramics

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Application of Electroceramics

• EBB 443-Technical Ceramics
• Dr. Sabar D. Hutagalung
• School of Materials and Mineral Resources
  Engineering
• Universiti Sains Malaysia

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Capacitors

• The multilayer ceramic (MLC) capacitors.
• The MLCC structure consists of alternate layers
  of dielectric and electrode material.
• Each individual dielectric layer contributes
  capacitance to the MLCC as the electrodes
  terminate in a parallel configuration.
• The advances in preparation technology have made
  it possible to make dielectric layers lt1 ?m
  thick.

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Cut-away view of multilayer ceramic capacitor.
Schematic of a typical multilayer ceramic (MLC)
capacitor
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Applications of Ferroelectric Thin Films

• Ferroelectric thin films have attracted attention
  for applications in many electronic and
  electro-optic devices.
• Applications of ferroelectric thin films utilize
  the unique dielectric, piezoelectric,
  pyroelectric, and electro-optic properties of
  ferroelectric materials.
• Some of the most important electronic
  applications of ferroelectric thin films include
  nonvolatile memories, thin films capacitors,
  pyroelectric sensors, and surface acoustic wave
  (SAW) substrates.
• The electro-optic devices include optical
  waveguides and optical memories and displays.

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Ferroelectric Memories

• Semiconductor memories such as DRAM SRAM
  currently dominate the market.
• However, the disadvantage of these memories is
  that they are volatile, i.e. the stored
  information is lost when the power fails.
• The non-volatile memories available at this time
  include complementary metal oxide semiconductors
  (CMOS) with battery backup and electrically
  erasable read only memories (EEPROM's).
• These non-volatile memories are very expensive.

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FeRAM Cross Section
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FeRAM

• FeRAM is a type of nonvolatile RAM that uses a
  ferroelectric film as a capacitor for storing
  data.
• FeRAM can achieve high-speed read/write
  operations comparable to that of DRAM, without
  losing data when the power is turned off (unlike
  DRAM).
• In addition to nonvolatility and high-speed
  operation, FeRAM cells offer the advantages of
  easy embedding into VLSI logic circuits and low
  power consumption, perhaps their greatest
  advantage for many applications.

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FeRAM

• FeRAM-embedded VLSI circuits have been used in
• smart cards,
• radio frequency identification (RFID) tags,
• and as a replacement for BBSRAM (battery
  backed-up static RAM), which is used in various
  devices to protect data from an unexpected power
  failure, as well as in many other SoC (system on
  a chip) applications.

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FeRAM

• A memory cell, where one bit of data is stored,
  is composed of a cell-selection transistor and a
  capacitor for 1T1C (one transistor, one
  capacitor)-type FeRAM.
• A major problem encountered when reducing the
  size of the memory cell is preventing reliability
  degradation.
• The reliability of FeRAM cells is dependent on
  the
• materials used (ferroelectric film, electrode,
  interlayer dielectric, etc.),
• fabrication process,
• device structure,
• memory cell circuit, and
• operation sequence.

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Schematic drawings of field-effect transistors
(FETs) with (a) metalferroelectricinsulatorsemi
conductor (MFIS) and (b) metalferroelectricmetal
insulatorsemiconductor (MFMIS) gate structures.
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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 leakage
  current is localized around weak spots in the
  film this is important in prolonging the data
  retention time.
• In other words, in an MFIS structure, the effect
  of the leakage current spreads out to the whole
  floating gate, and the charge neutrality is
  completely destroyed in a short time. Thus, an
  MFIS structure is superior in this regard.

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MFMIS structures

• In an MFMIS structure, it is possible to optimize
  the area ratio between the ferroelectric and
  buffer layer capacitors, so that the induced
  charges on both capacitors match.
• In an MFMIS structure, the floating gate material
  can be so chosen that a highquality ferroelectric
  film is formed on the floating gate and that
  constituent elements in the ferroelectric film do
  not diffuse into the buffer layer and Si
  substrate.

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Electro-optic Applications

• The requirements for using ferroelectric thin
  films for electro-optic applications include an
  optically transparent film with a high degree of
  crystallinity.
• The electro-optic thin film devices are of two
  types one in which the propagation of light is
  along the plane of the film (optical waveguides)
  and the other in which the light passes through
  the film (optical memory and displays).

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Other Ferroelectric Thin Film Applications

• Thin Film Capacitors
• The high dielectric permittivity of ferroelectric
  ceramics such as BaTiO3, PMN and PZT very useful
  for capacitor applications.
• The MLC capacitors have a very high volumetric
  efficiency (capacitance per unit volume) because
  of the combined capacitance of thin ceramic tapes
  ( 10-20 m m) stacked one on top of the other.

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• Pyroelectric Detectors
• Pyroelectricity is the polarization produced due
  to a small change in temperature.
• Single crystals of triglycine sulfate (TGS),
  LiTaO3, and (Sr,Ba)Nb2O6 are widely used for heat
  sensing applications.
• PbTiO3, (Pb,La)TiO3 and PZT have been widely
  studied for thin film pyroelectric sensing
  applications.

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• Surface Acoustic Wave Substrates
• SAW devices are fabricated by depositing
  interdigital electrodes on the surface of a
  piezoelectric substrate.
• An elastic wave generated at the input
  interdigital transducer (IDT) travels along the
  surface of the piezoelectric substrate and it is
  detected by the output interdigital transducer.
• These devices are mainly used for delay lines and
  filters in television and microwave communication
  applications.

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Schematic representation of the generation,
propagation and detection of surface acoustic
waves (SAW) on a piezoelectric substrate with
interdigital electrode.
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Gas Ignitors

• It consists of two oppositely poled ceramic
  cylinders attached end to end in order to double
  the charge available for the spark.
• The compressive force has to be applied quickly
  to avoid the leakage of charge across the
  surfaces of the piezoelectric ceramic.
• The generation of the spark takes place in two
  stages. The application of a compressive force
  'F' on the poled ceramic (under open circuit
  conditions) leads to a decrease in the length by
  dLD.
• The potential energy developed across the ends
  must be higher than the breakdown voltage of the
  gap, for sparking to occur.

A piezoelectric spark generator
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Gas Ignitors

• When the spark gap breakdown occurs the second
  stage of energy generation starts.
• The electric discharge across the gap results in
  a change from open circuit conditions to closed
  circuit conditions with the voltage dropping to a
  lower level.
• The combination of the strains from the open and
  short circuit conditions produce more energy that
  can be dissipated in the spark.
• Usually PZT ceramic disks are used for this
  application.

A piezoelectric spark generator
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Actuators Sensors
Schematic description of the geometry and the
working principle of the piezoelectric film
applied in actuators and sensors.
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Actuators Sensors

• An important family of functional materials are
  ferroelectrics or, more generally, polar
  materials.
• Their piezoelectricity can be used in sensors,
  actuators, and transducers
• Their pyroelectricity is employed in infrared
  detectors.

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Piezoelectric Microactuator Devices
Schematic drawing of self-actuation cantilever
with an integrated piezoresistor.
Schematic draw of optical scanning device with
double layered PZT layer (a) and the fabricated
device, (b) Mirror plate 300300 (µm2, DPZT
beam 800 230 µm2).
Micropump using screen-printed PZT actuator on
silicon membrane. (Courtesy of Neil White, Univ.
of Southampton, UK.)
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Aplication of Magnetic Ceramics

• Entertainment electronic (Radio, TV)
• Computer
• Microwave applications (Radar, communication,
  heating)
• Recording Tape
• Permanent motor

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Aplication of Magnetic Ceramics

• Spinel (cubic ferrites) Soft magnets
• Garnet (rare earth ferrites) Microwave devices
• Magnetoplumbite (hexagonal ferrites) Hard magnets

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Aplication of Soft Magnetics

• In the soft magnetic materials, only a small
  field is necessary to cause demagnetization and
  very small energy losses occur per cycle of
  hysteresis loop.
• This is important for applications such as
  transformers used in touch tone telephones or
  inductors or magnetic memory cores.
• During used a soft ferrites has its magnetic
  domains rapidly and easily realigned by the
  changing magnetic field.

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Aplication of Hard Magnetics

• A hard (or permanent) ceramic magnet achieves its
  magnetization during manufacture.
• The magnetic domains are frozen in by poling in
  an applied magnetic field as the material is
  cooled through its Tc.
• The materials are magnetically very hard and will
  retain in service the residual flux density, that
  remains after the strong magnetizing field has
  been removed.
• Hard ferrites are used in loudspeakers, motors.

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Aplication of Ferrites

• The cubic spinels, also called ferrospinels, are
  used as soft magnetic materials because of their
  very low coercive force of 4x10-5 weber/m2 and
  high saturation magnetization 0.3-0.4 weber/m2.
• (1 weber 1 volt-second 108 Maxwells)
• Flux density (induction) 1 Tesla 104 Gauss 1
  weber/m2. (1 Gauss 1 Maxwell/cm2).
• Hexagonal ferrites are hard magnetic materials
  with coercive force of 0.2 0.4 weber/m2 and
  large resistance to demagnetization, 2 3 J/m3.

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Aplication of Garnets

• Garnets are especially suited for high frequency
  microwave applications due to the ability to
  tailor properties such as magnetization, line
  width, g-factor, Tc, and temperature stability.
• The most common garnet ferrites are based upon
• 3Y2O3 5Fe2O3 or Y3Fe5O12 or YIG.

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Tape Recording

• Before passing over the record head, a tape
  passes over the erase head which applies a high
  amplitude, high frequency magnetic field to the
  tape to erase any previously recorded signal and
  to thoroughly randomize the magnetization of the
  magnetic emulsion.
• The gap in the erase head is wider than those in
  the record head the tape stays in the field of
  the head longer to thoroughly erase any
  previously recorded signal.

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Tape Recording

• High fidelity tape recording requires a high
  frequency biasing signal to be applied to the
  tape head along with the signal to "stir" the
  magnetization of the tape .
• This is because magnetic tapes are very sensitive
  to their previous magnetic history, a property
  called hysteresis.
• A magnetic "image" of a sound signal can be
  stored on tape in the form of magnetized iron
  oxide or chromium dioxide granules in a magnetic
  emulsion.
• The tiny granules are fixed on a polyester film
  base, but the direction and extent of their
  magnetization can be changed to record an input
  signal from a tape head.

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Electromagnet

• Electromagnets are usually in the form of iron
  core solenoids.
• The ferromagnetic property of the iron core
  causes the internal magnetic domains of the iron
  to line up with the smaller driving magnetiv
  field driving produced by the current in the
  solenoid.
• The solenoid field relationship is
• and k is the relative permeability of the iron,
  shows the magnifying effect of the iron core.

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Transformer

• A transformer makes use of Faradays law and the
  ferromagnetic properties of an iron core to
  efficiently raise or lower AC voltages.
• It of course cannot increase power so that if the
  voltage is raised, the current is proportionally
  lowered and vice versa.

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Transformer
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Applications of GMR

• The largest technological application of GMR is
  in the data storage industry.
• IBM were first to market with hard disks based on
  GMR technology although today all disk drives
  make use of this technology.
• On-chip GMR sensors are available commercially
  from Non-Volatile Electronics.
• It is expected that the GMR effect will allow
  disk drive manufacturers to continue increasing
  density at least until disk capacity reaches 10
  Gb per square inch.
• At this density, 120 billion bits could be stored
  on a typical 3.5-inch disk drive, or the
  equivalent of about a thousand 30-volume
  encyclopedias.

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Applications of GMR

• Other applications are as diverse as solid-state
  compasses, automotive sensors, non-volatile
  magnetic memory and the detection of landmines.

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Applications of GMR

• GMR also may spur the replacement of RAM in
  computers with magnetic RAM (MRAM).
• Using GMR, it may be possible to make thin-film
  MRAM that would be just as fast, dense, and
  inexpensive.
• It would have the additional advantages of being
  nonvolatile and radiation-resistant.
• Data would not be lost if the power failed
  unexpectedly, and the device would continue to
  function in the presence of ionizing radiation,
  making it useful for space and defense
  applications.

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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 Abelmann and J C Lodder, J. Phys. D
  Appl. Phys. 38 (2005) 363370

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Application of Superconductors

• Power lines.
• A significant amount of electrical energy is
  wasted as heat when electricity is transmitted
  down cables made of traditional metal conductors.
  
• Superconductors, can conduct electricity with
  zero resistance and would therefore be more
  efficient.
• Transport.
• Magnetically levitated trains already exist.
• Using superconducting magnets, cheaper, faster
  and more efficient variants could be produced.
• Electronics.
• By harnessing the Josephson effect, extremely
  fast electronic switches could be constructed,
  allowing faster microprocessors to be built.

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Microwave Dielectrics

• The Microwave materials including of dielectric
  and coaxial resonators to meet the demands of
  microwave applications for high performance, low
  cost devices in small, medium and large
  quantities.
• Applications
• Patch antennas
• Resonators /inductors
• Substrates
• C-band resonator-mobile
• Filters

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Dielectric Resonator (DR)

• Used in shielded microwave circuits, such as
  cavity resonator, filters and oscillators.
• Application as antenna in microwave and
  millimeter band.
• Advantages of DR
• light weight, low cost, small size, high
  radiation efficiency, large bandwidth.

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High-K dielectric to reduce size

• Dielectric Resonator (DR) size is inversely
  proportional to the frequency
• Larger ?, lower frequency
• Larger ?, smaller size

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• Photograph of split post dielectric resonators
  operating at frequencies 1.4, 3.2 and 33 GHz.
• Jerzy Krupka, Journal of the European Ceramic
  Society 23 (2003) 26072610

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