PPT on piezoelectric materials

1. Piezoelectric
Materials

2. Direct Piezoelectric Effect
Piezoelectric Material will generate electric potential
when subjected to some kind of mechanical stress.

3. The direct Effect : Generator
 Compression
Effect: Decrease in volume
and it has a voltage with
the same polarity as the
material
 Tension
Effect: Increase in volume
and it has a voltage with
opposite polarity as the
material
F
F

4. Inverse Piezoelectric Effect
If the piezoelectric material is exposed to an electric
field (voltage) it consequently lengthens or shortens
proportional to the voltage.

5. The Inverse Piezoelectric Effect
 If the applied voltage has
the same polarity then the
material expands.
 If the applied voltage has
the opposite polarity then
the material contracts.

6. The History of Piezo
 The name Piezo
originates from the
Greek word piezein,
which means to
squeeze or press.
 The piezoelectric
effect was first proven
in 1880 by the
brothers Pierre and
Jacques Curie.

7. Developing theories…
 Pierre and Jacques Curie predicted and
demonstrated the piezoelectric effect using tinfoil,
glue, wire, magnets, and a jeweler’s saw.
 They showed that crystals of tourmaline, quartz,
topaz, cane sugar, and Rochelle salt generate
electrical polarization from mechanical stress.
 The converse effect was mathematically derived by
Gabriel Lippman in 1881 using fundamental
thermodynamic principles and was later
experimentally confirmed by the Curies.

8. How are Piezoelectric
ceramics made?
 Fine powders of the component metal oxides are
mixed in specific proportions, then heated to
form a uniform powder.
 The powder is mixed with an organic binder and
is formed into structural elements.
 The elements are fired according to a specific
time and temperature program, during which the
powder particles sinter and the material attains a
dense crystalline structure.
 The elements are cooled, then shaped or trimmed
to specifications. Electrodes are applied to a
conducting material, which is connected to the
elements.

9. Crystal Structure and
Dipole Moments
 A traditional piezoelectric ceramic is a
mass of perovskite crystals. Each crystal
consists of a small tetravalent metal ion,
usually titanium or zirconium, in a lattice
of larger divalent metal ions, usually lead
or barium, and O2- ions
 At temperatures below the Curie point,
however, each crystal has tetragonal or
rhombohedral symmetry and a dipole
moment. Above the Curie point each
perovskite crystal in the fired ceramic
element exhibits a cubic symmetry with
no dipole moment.

10. Polarizing Piezoelectric Material
 Adjoining dipoles form regions of local alignment called domains.
The alignment gives a net dipole moment to the domain, and thus a
net polarization. The direction of polarization among neighboring
domains is random, however, so the ceramic element has no overall
polarization.
 The domains in a ceramic element are aligned by exposing the
element to a strong, direct current electric field, usually at a
temperature slightly below the Curie point
 When the electric field is removed most of the dipoles are locked
into a configuration of near alignment

11. Types of Piezoelectric
Materials
 Naturally occurring crystals:
Berlinite (AlPO4), cane sugar, Quartz, Rochelle salt, Topaz,
Tourmaline Group Minerals, and dry bone (apatite crystals)
 Man-made crystals:
Gallium orthophosphate (GaPO4), Langasite (La3Ga5SiO14)
 Man-made ceramics:
Barium titanate (BaTiO3), Lead titanate (PbTiO3), Lead zirconate
titanate (Pb[ZrxTi1-x]O3 0<x<1) - More commonly known as PZT,
Potassium niobate (KNbO3), Lithium niobate (LiNbO3), Lithium
tantalate (LiTaO3), Sodium tungstate (NaxWO3), Ba2NaNb5O5,
Pb2KNb5O15
 Polymers:
Polyvinylidene fluoride (PVDF)

12. Sonic and Ultrasonic Applications
 Sonar with Ultrasonic
time-domain
reflectometers
 Materials testing to detect
flaws inside cast metals
and stone objects as well
as measure elasticity or
viscosity in gases and
liquids
 Compact sensitive
microphones and guitar
pickups.
 Loudspeakers

13. Pressure Applications
 Transient pressure measurement to
study explosives, internal combustion
engines (knock sensors), and any
other vibrations, accelerations, or
impacts.
 Piezoelectric microbalances are used
as very sensitive chemical and
biological sensors.
 Transducers are used in electronic
drum pads to detect the impact of the
drummer's sticks.
 Energy Harvesting from impact on the
ground
 Atomic force and scanning tunneling
microscopes.
 Electric igniters and cigarette lighters

14. Consumer Electronics Applications
 Quartz crystals resonators as
frequency stabilizers for
oscillators in all computers.
 Phonograph pick-ups
 Accelerometers: In a
piezoelectric accelerometer a
mass is attached to a spring
that is attached to a
piezoelectric crystal. When
subjected to vibration the
mass compresses and
stretches the piezo electric
crystal. (iPhone)

15. Motor Applications
 Piezoelectric elements can be
used in laser mirror alignment,
where their ability to move a large
mass (the mirror mount) over
microscopic distances is exploited.
By electronically vibrating the
mirror it gives the light reflected
off it a Doppler shift to fine tune
the laser's frequency.
 The piezo motor is viewed as a
high-precision replacement for
the stepper motor.
 Traveling-wave motors used for
auto-focus in cameras.