EBB 443 Seramik Teknikal

Part 1 Prof. Zainal Arifin Ahmad Part 2 Dr. Hasmaliza Part 3 Electroceramics Dr. Julie

NoTopic ContentsTeaching weeks (2 hrs/week) 1.Introduction to electroceramics1 2.Type & properties of electroceramics 2, 3 3.Application of electroceramics4 4.Processing of electroceramics5 5.Testing & characterization of electroceramic products 5

 A. J. Moulsen & J. M. Herbert, Electroceramics: Materials, properties, application, 2 nd Edition, John Wiley & Sons,  L.L. Hench and J.K. West, Principles of electronic ceramics, John Wiley & Sons,  K. Uchino, Ferroelectric Devices, Marcel Dekker, 2000.

 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 (natural) physical properties of ceramics has made them desirable for use in wide range of industries, with their first applications in the electronics sector.

 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 modified to operate as insulators, ferroelectric materials, highly conductive ceramics, electrodes as well as sensors and actuators.

 The applications of ceramics in the electronics industry can be divided into two groups: ◦ for interconnection and packaging of semiconductor circuits ◦ in circuit components such as capacitors and sensors.

 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

Ceramic insulators

Bulk Ceramic Thermistors Bulk Ceramic Varistors (VDR-voltage dependent resistors)

Bulk ceramic resistors

 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?

 Chip Monolithic ceramic capacitors  Microwave Oscillators  Microwave Filters  Ceramic Resonators  High Frequency SAW Filter  Ceramic Filters  Piezoelectric Receivers  Piezoelectric Speakers

Johanson Dielectrics Capacitor Products: Ceramic SMT and Leaded High Voltage and High Temperature, Dual and Multi Capacitor Arrays, Low Inductance, X2Y, Switchmode.

 The discovery of materials with unusually high-dielectric constants (  r > ,0000), and their ferroelectric nature, led to an explosion in ceramic use.

Can fulfill various function in electrical circuits including blocking, a.c-d.c separation, filtering and energy storage e.g as charge storage – in a photoflash unit of a camera

C = "capacitance" = q /  V Units: Coulomb/Volt = Farad (F) The capacitance of a capacitor is constant; if q increases,  V increases proportionately. Michael Faraday ( )

Q = CV Q: charge (Coulomb) C: capacitance (Farad) V: potential difference (Volt) d: separation/thickness (meter)  o : permitivity of vacuum = 8.854x C 2 /m 2 or F/m  r : dielectric constant

- Various geometrical forms i.e. disc, tubes and multilayer - Multilayer ceramic capacitor (MLCC) was introduced in the early part of World War II - objectives: (a) to reduce the sizes and increases capacitance values (b) cost reduction

 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.

Cut-away view of multilayer ceramic capacitor.

Surface-Mount Ceramic Capacitors Military electronics

 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).  NTC- As the temperature rises, more charge carriers become available and the resistance falls.  PTC- show an increase in resistance with temperature

 How could you make a sensor circuit for use in a fire alarm?

 You want a circuit which will deliver a HIGH voltage when hot conditions are detected.  You need a voltage divider with the ntc thermistor

 How could you make a sensor circuit to detect temperatures less than 4°C to warn motorists that there may be ice on the road?

 You want a circuit which will give a HIGH voltage in cold conditions  So?

 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".

 Give one or more example of piezoelectric application in electronic circuit

 This kind of material has perovskite structure, with general formula ABO 3, in which ◦ A is a large divalent metal ion such as Pb 2+ or Ba 2+, ◦ B is a small tetravalent metal ion, such as Ti 4+ or Zr 4+, octahedrally coordinating with oxygen.  Ferroelectricity occurs due to the displacement of positive ions B 4+ and negative ions O 2- in opposite directions.

 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).

Examples of piezoelectric microsensors on silicon: (a) microphone and (b) accelerometer. (OPA N.V., Taylor and Francis Ltd.)

 There are various types of magnetic material classified by their magnetic susceptibilities: diamagnetic, paramagnetic and ferromagnetic.  Diamagnetic, have very small negative susceptibilities (about ).  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 – ).

Transformer

 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.

 In a group of 6 or 7, discuss about the given topic and prepare the presentation slide.  The presentation duration should be not more than 20 minutes/group  The presentation session will be held on week 14

Find the application of these electroceramic. Support with figures and videos 1.Ceramic insulators 2.High-k ceramic dielectrics 3.Piezoelectric ceramics 4.Ferroelectric ceramics 5.Magnetic ceramics 6.Superconductors 7.Photonic ceramics