A presentation on Piezoelectricity by JaTin. Including what is piezoelectricity, how and why it happens, applications, and detailed application of quartz watches.

1. PIEZOELECTRICITY
SEC ASSIGNMENT: JIGYASU SAINI 19/953

2. WHAT IS PIEZOELECTRICITY ?
Piezoelectricity is the electric charge that
accumulates in certain solid materials (such
as crystals, certain ceramics, and biological
matter such as bone, DNA and
various proteins in response to
applied mechanical stress. The
word piezoelectricity means electricity
resulting from pressure and latent heat. It is
derived from the Greek word piezein, which
means to squeeze or press, and ēlektron,
which means amber, an ancient source of
electric charge.
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3. WHAT CAUSES
PIEZOELECTRICITY ?
There are some selected set of
materials/crystals which when being
subjected to a deforming forces, are
capable of giving rise to an electric
current.
Certain crystals, such as Rochelle’s salt
on applying pressure will deform it’s
crystalline structure.
In the initial condition when no force acts
on the crystal, the charges on the crystal
are so aligned that the net charge will be
equal to 0.
However, on application of a force
resulting in the deformation of the crystal,
the charges on the crystal will tend to
separate such that one end will be
positively charged and the other end of
the crystal will be negatively charged.
If the crystals are oriented accordingly,
we can cause efficient charge separation
which can be tapped by connecting the
arrangement through a closed circuit and
this will thus cause flow of current through
the circuit.
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4. WHAT CAUSES PIEZOELECTRICITY: AN EXAMPLE OF QUARTZ
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+
-
-
+
-
+
+
-
-
+
-
+
+
-
-
+
-
+
Consider the hex structure of a Quartz crystal, with Oxygen atoms having little negative charge and Silicon atoms having
little bit positive charge.
When no pressure
is applied, the
center of net
negative charge is
at the center of
charge
When no pressure is applied, the
center of net positive charge is
at the center of charge
+
-
-
+
-
+
The net positive and
net negative charge
overlaps each other
and creates the
molecule electrically
neutral.
When pressure is applied, the
top +ve atom get pushed
down and other two +ve
atom get pushed outwards,
this makes the center of net
+ve charge move slightly
downwards.
+
-
-
+
-
+
When pressure is applied, the
bottom -ve atom get pushed
up and other two -ve atom
get pushed outwards, this
makes the center of net -ve
charge move slightly
upwards.
This makes +ve charge shift in
one direction and negative
charge shift in another
direction, making element
gain some net potential
difference.

5. 5
Piezoelectric materials
There are many materials, both natural and man-made, that exhibit a range of piezoelectric effects.
Berlinite
(structurally
identical to
quartz)
Cane Sugar
Quartz
Rochelle
salt
Topaz
Tourmaline
(Tourmaline is a
six-member ring
cyclosilicate
having a trigonal
crystal system.)
Bone
(dry bone exhibits some
piezoelectric properties due
to the apatite crystals)
Barium Titanate
and
Lead Zirconate Titanate
(Man-Made)
In recent years, due to the growing
environmental concern regarding
toxicity in lead-containing devices
there has been a push to develop
lead free piezoelectric materials. To
date, this initiative to develop new
lead-free piezoelectric materials has
resulted in a variety of new
piezoelectric materials which are
more environmentally safe.

6. APPLICATIONS
Due to the intrinsic characteristics of piezoelectric materials,
there are numerous applications that benefit from their use:
High Voltage and Power
Sources
An example of applications in this
area is the electric cigarette lighter,
where pressing a button causes a
spring-loaded hammer to hit a
piezoelectric crystal, thereby
producing a sufficiently high voltage
that electric current flows across a
small spark gap, heating and igniting
the gas. Most types of gas burners
and ranges have a built-in piezo
based injection systems.
Sensors
The principle of operation of a
piezoelectric sensor is that a
physical dimension, transformed
into a force, acts on two opposing
faces of the sensing element.
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The detection of pressure variations
in the form of sound is the most
common sensor application, which
is seen in piezoelectric microphones
and piezoelectric pickups for
electrically amplified guitars.
Piezoelectric sensors in particular
are used with high frequency sound
in ultrasonic transducers for medical
imaging and industrial
nondestructive testing.
Piezoelectric Sensor

7. QUARTZ CLOCK
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Time is the only dimension that controls everything in this world.
There is no start and end point of time scale. But we have assumed or marked the
years, months and days. For us sunrise, sunset, movement of moon etc. are time
scales. But in a day we need a clock to track the time accurately.
From starting days of civilization man try to track time with many concepts such as
sun clock, sands of time (hour glass). Then comes mechanical clock and pendulum
clock; but they shows many problems.
Then quartz clock came. We know that quartz is a piezoelectric material.
Before the mechanism of quartz clock we should know about the history of
quartz clock-
• 1927 – First quartz clock was built by Warren Marrison & J W Horton at Bell
Telephone laboratory.
• 1967 – First European Quartz clock for consumers by “Astrochone”.
• 1969 – First Quartz wrist watch by “Calibrer”, Japan .
• During 1980 due to development of solid state digital electronics it was possible
to make compact and inexpensive quartz clock.
Present days all the clocks, we are using, that may be digital, analog, wrist watch,
wall clock, are quartz clocks. Here is the figure showing internal parts of a quartz
wrist watch.

8. MECHANISM
Construction:
1. Battery.
2. Electric stepping motor.
3. Microchip.
4. Circuit connects microchip to other
components.
5. Quartz crystal oscillator.
6. Crown screw for setting time.
7. Gears turn hour, minute, and
second hands at different speeds.
8. Tiny central shaft holds hands in
place.
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Quartz is made of silicon dioxide (SiO2), and is a piezoelectric material.
Clocks use Quartz crystal oscillator, which looks like a simple circuit
component as capacitor or resistor but its internal structure is somewhat
different as shown in the figure on right
Various components of a basic
wrist watch
Uncased Quartz
crystal oscillator

9. WORKING
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Quartz crystal inside the oscillator is bifurcated like a tuning fork
The amazing cause that why quartz, not other piezoelectric crystal, is used in clock is –
when an electric pulse is applied, the crystal vibrate in a constant frequency that is
32,768Hz = 215
Hz. Because of reverse piezoelectric effect it also generates electric
pulse of same frequency.
As the frequency is the power of two, that can be easily converted to 1Hz frequency
digitally. 1Hz frequency is required to drive the second hand of a clock.
Overall mechanism is as described below
1) Battery provides current to input microchip circuit.
2) Input microchip circuit makes quartz crystal (precisely cut and shaped like a tuning
fork) oscillate (vibrate) 32768 times per second.
3) Output microchip circuit detects the crystal's oscillations and turns them into
regular electric pulses, one per second.
4) Electric pulses drive miniature electric stepping motor. This converts electrical
energy into mechanical power.
5) Electric stepping motor turns gears.
6) Gears sweep hands around the clock-face to keep time.
The above is the mechanism of how an analog watch works. But mechanism digital
clock is not different. In digital clock the output of second micro chip is given to seven
segment display and counters are used for minute and hour calculation.

10. 10
A question may arise in our mind that why the clock gain or lose time. Quartz
crystal has a constant vibration frequency of 32,768Hz, but this may vary up to
0.06Hz due to temperature change.
Due to this reason clock gains or lose small time.
Clock is not the only application of crystal oscillator, but all most every digital
system requires a frequency standard to run hence they also use crystal oscillator
of different size and different frequency rating. Some of them and the internal
structure is shown in these images.
WHY CLOCKS GAIN OR LOSE TIME ?

11. THANK YOU
SUBMITTED TO: KRISHAN KUMAR SIR.