its about piezoelectricity and its applications. And Advantages and Disadvantages And Conclusion.

1. Piezoelectricity and
its applications
Mughees Khan (BEE-FA13-124)
Haseeb Rehman (BEE-FA13-057)
Uzair (BEE-FA13-030)
Usama Khalid (BEE-FA13-073)

2. What is piezoelectricity?
Piezoelectricity is the electric charge that accumulates in certain solid materials
in response to applied mechanical stress. The word piezoelectricity means
electricity resulting from pressure.
The piezoelectric effect is understood as the linear electromechanical
interaction between the mechanical and the electrical state in crystalline
materials with no inversion symmetry. The piezoelectric effect is a reversible
process in that materials exhibiting the direct piezoelectric effect (the internal
generation of electrical charge resulting from an applied mechanical force)
also exhibit the reverse piezoelectric effect (the internal generation of a
mechanical strain resulting from an applied electrical field). For example, lead
zirconate titanate crystals will generate measurable piezoelectricity when their
static structure is deformed by about 0.1% of the original dimension.
Piezoelectricity is found in useful applications such as the production and
detection of sound, generation of high voltages, electronic frequency
generation, microbalances, to drive an ultrasonic nozzle, and ultrafine focusing
of optical assemblies. Examples of such materials will be described later.

4. Mechanism of Piezoelectricity
The nature of the piezoelectric effect is closely related to the occurrence of
electric dipole moments in solids. The latter may either be induced for ions on
crystal lattice sites with asymmetric charge surroundings (as in BaTiO3 and
PZTs) or may directly be carried by molecular groups (as in cane sugar). The
dipole density or polarization (dimensionality [Cm/m3
] )may easily be
calculated for crystals by summing up the dipole moments per volume of the
crystallographic unit cell. As every dipole is a vector, the dipole density P is a
vector field. Dipoles near each other tend to be aligned in regions called Weiss
domains. The domains are usually randomly oriented, but can be aligned using
the process of poling (not the same as magnetic poling), a process by which a
strong electric field is applied across the material, usually at elevated
temperatures. Not all piezoelectric materials can be poled.

5. • Piezoelectricity is the combined effect of the electrical
behaviour of the material
D= εE
• where D is the electric charge density displacement, ε is
permittivity and E is electric field strength.

6. • Output Power from PiezoElectric Materials
The output voltage obtained from a single piezoelectric crystal is in
millivolt(mV) range, which is different for different crystals.
• And the wattage is in microwatt(mW)
• In order to produce higher voltages, the piezoelectric materials can be
arranged in series.
• It is used to power backup supplies or to power low-power microprocessors

7. Materials
Many materials, both natural and synthetic, exhibit piezoelectricity:
• Naturally Occuring
 Quartz
 Sucrose
 Topaz
 Lead Titanate (PbtiO3)
• Synthetic Ceramics
 Barium titanate(BaTiO3)(first piezoelectric ceramic)
 Zinc Oxide:
Polycrystalline (ceramic) ZnO with randomly oriented grains exhibits no
piezoelectric effect.Ceramics and polycrystalline thin films of ZnO may exhibit
macroscopic piezoelectricity only if they are textured (grains are preferentially
oriented), such that the piezoelectric responses of all individual grains do not
cancel. This is readily accomplished in polycrystalline thin films.

8. Piezoelectric Sensors
A piezoelectric sensor is a device that uses the piezoelectric effect, to
measure changes in pressure, acceleration, temperature, strain or force by
converting them to an electrical charge. The prefix piezo- is Greek for 'press'
or 'squeeze'.
• One disadvantage of piezoelectric sensors is that they cannot be used for truly
static measurements.
Sensor design
Based on piezoelectric technology various physical quantities can be measured;
the most common are pressure and acceleration. For pressure sensors, a thin
membrane and a massive base is used, ensuring that an applied pressure
specifically loads the elements in one direction.
Various sensor application include :
• Piezoelectric elements are also used in the detection and generation of sonar waves
• Power monitoring in high power applications (e.g. medical treatment, sonochemistry
and industrial processing)
• Piezoelectric microbalances are used as very sensitive chemical and biological sensors

9. • Reduction of vibrations and noise
Different teams of researchers have been investigating ways to reduce vibrations in
materials by attaching piezo elements to the material. When the material is bent by a
vibration in one direction, the vibration-reduction system responds to the bend and
sends electric power to the piezo element to bend in the other direction. Future
applications of this technology are expected in cars and houses to reduce noise.
Further applications to flexible structures, such as shells and plates, have also been
studied for nearly three decades.
• Surgery
A recent application of piezoelectric ultrasound sources is piezoelectric surgery, also
known as piezosurgery. Piezosurgery is a minimally invasive technique that aims to cut
a target tissue with little damage to neighboring tissues. For example, its use in hand
surgery for the cutting of bone, using frequencies in the range 25–29 kHz, causing
microvibrations of 60–210 μm. It has the ability to cut mineralized tissue without
cutting neurovascular tissue and other soft tissue, thereby maintaining a blood-free
operating area, better visibility and greater precision.

10. • Floor Mats And People Powered Dance Clubs
• Series of crystal can be laid below the floor mats,tiles and carpets.
• One footstep can only provide enough electrical current to light two 60-watt
bulbs for one second.
• When mob uses the dance floor, an enormous voltage is generated.
• This energy is used to power the equipment of nightclubs.

11. • Mobile Keypads And Keyboards
• Crystals laid down under the keys of mobile unit and keyboard.
• For every key pressed vibrations are created.
• These vibrations can be used for charging purposes.

12. • Gyms and workplaces
• Vibrations caused from machines in the gym.
• At workplaces, piezoelectric crystal are laid in the chairs for storing energy.
• Utilizing the vibrations in vehicle like clutches, gears etc.

13. Advantages and disadvantages of
Piezoelectricity
Advantages
•Unaffected by external
electromagnetics fields.
•Pollution free.
•Low maintenance.
•Easy replacement of
equipment.
Disadvantages
• They cannot be used for truly
statics measurements.
• Can pick up stray voltages in
connecting wires.
• Crystal is prone to crack if
overstressed.
• May get affected by long use
at high temperatures.

14. • Conclusion
• Flexible piezoelectric materials are attractive for power harvesting apllications
because of their ability to withstand large amount of strain.
• Convert the ambient vibration energy surrounding them into electrical energy.
• Electrical energy can then be used to power other devices or stored for later
use.