Piezo electric property

BY,K.M.BhartheXI-B

INTRODUCTION

Piezo electricity is defined as a change in electric polarisation

with a change in applied stress.

INTRODUCTION

The word piezo is Greek for "push“.

Crystals which acquire a charge when compressed, twisted or

distorted are said to be piezoelectric. This provides a convenient transducer effect

between electrical and mechanical oscillations.

INTRODUCTION

The converse of piezo electric effect is the change of strain or

stress in a material due to an applied electric field.

discovery

It was discovered in 1880 by Jaques and Pierre Curie during

studies into the effect of pressure on the generation of electric

charge by crystals (such as quartz)

internal mechanism

• The effect is explained by the displacement of ions in crystals

that have a nonsymmetrical unit cell

• When the crystal is compressed, the ions in each unit cell are

displaced, causing the electric polarization of the unit cell.

internal mechanism

• Because of the regularity of crystalline structure, these

effects accumulate, causing the appearance of an electric

potential difference between certain faces of the crystal.

• When an external electric field is applied to the crystal, the ions

in each unit cell are displaced by electrostatic forces, resulting in

the mechanical deformation of the whole crystal.

internal mechanism

Pictorial demonstration

internal mechanism

• In simple words, Piezoelectric materials are crystalline solids whose asymmetric

structures create an electric dipole moment in the crystal lattice, which is

sensitive to both elastic strain and applied electrical field.

• When an electrical field is applied to a piezoelectric material, a stress is

induced and the material changes shape (called the piezoelectric effect).

Examples of piezo electric materials

Piezoelectric materials can be divided in 2 main groups: crystals and ceramics.

CrystalsQuartz SiO2

Gallium orthophosphateCeramics

Barium Titanate BaTiO3 Lead Zirconate Titanate PZT

PolymersPolyvinylidene DiFluoride PVDF

Working of quartz crystals

Quartz crystals have piezoelectric properties, meaning that they are capable of changing a mechanical

force into electricity, or an electric current into a mechanical force. A

slice, or wafer, of quartz crystal will generate an electric current when it is subjected to pressure.

Working of quartz crystals

Working of quartz crystals

This property is used in quartz watches and clocks,which have an

accuracy of one second in every 10 seconds.

9

Other examples The reverse piezoelectric effect is utilised in

printing equipment, both in the home and on industrial production lines.

Simple speakers,watch beepers, portable stereo systems, and in mobile phones and computers. In ultrasonic transducers, used for medical

ultrasound imaging TV remote controls and echolocation devices used

to help drivers park their car. Piezoceramic filters are used in:

Radios and televisionsWatch bleepers

Battery operated smoke detector alarms

Pros• Have a high Stiffness value

and produce a high output with very little strain

• Ideal for rugged use.• Excellent linearity over a

wide amplitude• Ideal for continuous online

condition monitoring smart systems.

Cons• Can be used only for dynamic

pressure sensing as in case of static sensing the signals will decay away

• Operation over long cables may affect frequency response and introduce noise and distortion, the cables need to be protected.

Future applications

• New applications and potential uses of piezoelectric components are being identified in a

number of different fields.

• Piezoelectric components’ durability and low cost mean that as research and development continues,

the range of commercial applications will also continue to grow rapidly.

• The market for piezoelectric components is expected to see double digit growth in the next

five years. New devices such as piezoelectric generators will see the highest growth, estimated

at 51.5% annually.

Thanks for

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