Introduction to Electroceramics

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Introduction to Electroceramics

• EBB 443
• Seramik Teknikal

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Ceramic Materials

• Ceramic materials can now be broadly considered
  to be all inorganic non-metallic materials. 
• However, it is more useful to classify them as
  polycrystalline non-metallic materials. 
• The inherent physical properties of ceramics has
  made them desirable for use in wide range of
  industries, with their first applications in the
  electronics sector.

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Introduction to Ceramics Concept
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Evolution of Materials and Ceramics
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Pottery and Electroceramics
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Electroceramics
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What are electroceramics?

• The term Electroceramic is used to describe
  ceramic materials that have been specially
  formulated for specific electrical, magnetic, or
  optical properties.
• Their properties can be tailored to operation as
  insulators, ferroelectric materials, highly
  conductive ceramics, electrodes as well as
  sensors and actuators.
• The performance of electroceramic materials and
  devices depends on the
• complex interplay between processing,
• chemistry,
• structure at many levels and
• device physics.

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What are electroceramics?

• The applications of ceramics in the electronics
  industry can be divided into two groups
• the use of materials for interconnection and
  packaging of semiconductor circuits, and
• the use of ceramics in circuit components which
  perform a function in their own right, such as
  capacitors and sensors.
• The former application forms a large market and
  has been well reviewed elsewhere.
• The latter is particularly interesting because
  the materials which are used for a very wide
  range of applications are in many cases closely
  related in crystal structure.

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Common Applications for Electroceramics

• Insulator
• Resistor
• High dielectric constant capacitors
• Piezoelectric sonar transducers
• Ultrasonic transducers
• Radio communication filters
• Medical diagnostic transducers
• Ultrasonic motors
• Electro-optic light valves
• Thin-film capacitors
• Ferroelectric thin-film memories

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Ceramic insulators
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Bulk Ceramic Varistors (VDR-voltage dependent
resistors)
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Bulk ceramic resistors
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Cellular Telephone

• Portable communication devices such as cordless,
  portable, and car telephone have become popular
  worlwide.
• Do you know what kind of dielectric and
  ferroelectric components are used in a cellular
  phone?

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Cellular Telephone

• Chip Monolithic ceramic capacitors
• Microwave Oscillators
• Microwave Filters
• Ceramic Resonators

• High Frequency SAW Filter
• Ceramic Filters
• Piezoelectric Receivers
• Piezoelectric Speakers

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Johanson Dielectrics Capacitor Products Ceramic
SMT and Leaded High Voltage and High Temperature,
Dual and Multi Capacitor Arrays, Low Inductance,
X2Y, Switchmode.
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Capacitors
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Capacitors
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Capacitors
C "capacitance"    q /DV Units  Coulomb/Volt            Farad (F)-----------------------------The capacitance of a capacitor is constant if q increases, DVincreases proportionately.                    Michael Faraday           (1791-1867)
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Q CV Q charge (Coulomb) C capacitance
(Farad) V potential difference (Volt) d
separation/thickness (meter) ?o permitivity of
vacuum 8.854x10-12 C2/m2 or F/m ?r
dielectric constant
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Dielectric Materials and Devices
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Multilayer Ceramic Capacitor

• The demands for miniaturization largely preclude
  an increase in the face area A.
• One exception is the multilayer ceramic capacitor
  (MLCC), in which case
• where N is the number of stacked plates.
• Ideally, the dielectric should have a low
  electrical conductivity so that the leakage
  current is not too large.

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Multilayer Ceramic Capacitor
Cut-away view of multilayer ceramic capacitor.
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Surface-Mount Ceramic Capacitors

Military electronics
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Surface-Mount Capacitors

• Ceramic surface-mount capacitors are used in
  every type of electronic equipment including
  computers, telecommunication, automotive
  electronics, military electronics, medical
  electronics and consumer electronics.
• High voltage and high temperature ceramic
  capacitors are serve military, aerospace, oil
  service, oil exploration and other markets
  including medical imaging, power generation, and
  high voltage power supply.

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Temperature Sensitive Resistor

• There are numerous uses for resistors with high
  valuea of the temperature coefficient of
  resistance (TCR) and they may be negative (NTC)
  or positive (PTC).

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Voltage-dependent Resistors (Varistors)

• There are a number of situations in which it is
  valuable to have a resistor which offers a high
  resistance at low voltages and a low resistance
  at high voltages.
• Such a devices can be used to protect a circuit
  from high-voltage transients by providing a path
  across the power suply that
• takes only a small current under normal
  conditions but takes large current if the voltage
  rises abnormally,
• thus preventing high-voltage pulses from reaching
  the circuit.
• Schematic use of a VDR to protect a circuit
  against transients,

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Schematic representation of varistor-capacitor
device construction and its equivalent circuit.
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High-K Dielectric Materials

• The discovery of materials with unusually
  high-dielectric constants (?r gt 2000-100000), and
  their ferroelectric nature, led to an explosion
  in ceramic use. 
• The first employed in high-k capacitors is BaTiO3
  based, and later developed into
• piezoelectric transducers,
• positive temperature coefficient (PTC) devices,
  and
• electro-optic light valves. 
• Recent developments in the field of ferroelectric
  ceramics is their use in
• medical ultrasonic composites,
• high displacement piezoelectric actuators, and
• photoresistors.

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Piezoelectric

• Piezoelectricity was discovered in 1880 by J P
  Curie during studies into the effect of pressure
  on the generation of electrical charge by
  crystals (such as quartz). 
• Described as the generation of electricity as a
  result of mechanical pressure, or
• "electrical polarisation produced by mechanical
  strain in crystals belonging to certain classes".
  
• The phenomenon can be attributed to a lack of
  centre of symmetry in the crystallographic unit
  cell - or the unit cell is described as
  non-centrosymmetric. 

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Piezoelectric

• For Piezoelectricity - 
• the effect is linear and reversible,
• the magnitude of the polarisation is dependant on
  the magnitude of the stress,
• the sign of the charge produced is dependant on
  the type of stress (tensile or compressive).

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Piezoelectric Ceramics
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Piezoelectric Microactuator Devices
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).
Schematic drawing of self-actuation cantilever
with an integrated piezoresistor.
Micropump using screen-printed PZT actuator on
silicon membrane. (Courtesy of Neil White, Univ.
of Southampton, UK.)
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Ferroelectric ceramics

• This kind of material has perovskite structure,
  with general formula ABO3, in which
• A is a large divalent metal ion such as Pb2 or
  Ba2,
• B is a small tetravalent metal ion, such as Ti4
  or Zr4, octahedrally coordinating with oxygen.
• Ferroelectricity occurs due to the displacement
  of positive ions B4 and negative ions O2- in
  opposite directions.

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Ferroelectric Ceramics

• This displacement causes spontaneous polarisation
  which is the origin of many other properties such
  as
• extremely high dielectric constant,
• hysteresis loop (non-linear dependence of
  polarisation with applied field),
• piezoelectricity (the ability to change the
  dimension with applied field and to produce the
  current with applied mechanical stress).

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Ferroelectric ceramics PZT (PbZrTiO3) structure

• Ferroelectric ceramics are widely used in modern
  technology with various applications (sensors,
  actuators, generators, transducers to very recent
  IC for RAM).
• They can be used for DRAM (dynamic random access
  memory), and high remanent polarisation and low
  coercive field for being used as NVRAM
  (non-volatile random access memory).

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Examples of piezoelectric microsensors on
silicon (a) microphone and (b) accelerometer.
(OPA N.V., Taylor and Francis Ltd.)
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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.
• ApplicationsPatch antennasResonators/inductorsS
  ubstrates
• C-band resonator-mobile
• Filters

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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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EM Spectrum

• Mobile phones operate in two main frequency
  ranges
• In US - the older systems 850 MHz the newer
  1900 MHz.
• In European - near 900 MHz 1800 MHz (GSM).

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Magnetic Ceramics

• There are various types of magnetic material
  classified by their magnetic susceptibilities
  diamagnetic, paramagnetic and ferromagnetic.
• Diamagnetic, have very small negative
  susceptibilities (about 10-6).
• Example inert gases, hydrogen, many metals, most
  non-metals and many organic compounds.
• Paramagnetics are those materials in which the
  atoms have a permanent magnetic moment arising
  from spinning and orbiting electrons.
• The susceptibilities are therefore positive but
  again small (in range 10-3 10-6).

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Transformer
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Magnetic Ceramics- cont.

• Ferromagnetic materials are spontaneously
  magnetized below the Curie point.
• The spontaneous magnetization is not apparent in
  materials which have not been exposed to an
  external field because of the formation of small
  volumes (domains) of materials each having its
  own direction of magnetization.
• Spontaneous magnetization is due to the alignment
  of uncompensated electron spin by the strong
  quantum mechanical exchange forces.

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Giant Magnetoresistance (GMR)

• The GMR is the change in electrical resistance of
  some materials in response to an applied magnetic
  field.
• GMR effect was discovered in 1988 by two European
  scientists working independently
• Peter Gruenberg of the KFA research institute in
  Julich, Germany, and
• Albert Fert of the University of Paris-Sud .
• They saw very large resistance changes - 6
  percent and 50 percent, respectively - in
  materials comprised of alternating very thin
  layers of various metallic elements.
• These experiments were performed at low
  temperatures and in the presence of very high
  magnetic fields.

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Intrinsic Magnetoresistance

• SrRuO3
• Tl2Mn2O7
• CrO2
• La0.7(Ca1-ySry)0.3MnO3
• Fe3O4
• CaCu3Mn4O12 (CCMO)

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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.
• 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

• Read sensors that employ the GMR effect available
  for detecting the fields from tiny regions of
  magnetization.
• These tiny sensors can be made in such a way that
  a very small magnetic field causes a detectable
  change in their resistivity such changes in the
  resistivity produce electrical signals
  corresponding to the data on the disk.
• 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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