Anuraj Sunda

THE FUTURE SOURCE OF ENERGYPiezoelectric Materials A Presentation by  Anuraj Sunda 2014IMSPH003  CONTENTS 1.Introduction to piezoelectricity 2.Discovery and History 3.Cause of piezoelectricity 4.Types of piezoelectric materials 5.Application fields a).As a high voltage source b).Sensors c).Actuators d).As frequency standard e).Sonic and Ultrasonic f).Motor 6.Future Outlook 7.Energy harvesting INTRODUCTION TO PIEZOELECTRICITY  The word “piezoelectricity” is derived from a Greek word “pizo” or “piezein” which means to squeeze or press.  The conversion of mechanical energy into electrical one is generally achieved by means of electromagnetism (electro-magnetic induction). But there are other physical phenomena that can also convert mechanical energy into electricity directly, one of which is piezoelectricity.  Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress and reverse process is also possible.  Hence the piezoelectric effect exists in two domains.  Direct piezoelectric effect: Converts mechanical stress to emf  Reverse piezoelectric effect: Converts electrical energy to mechanical compression or expansion Piezoelectric effect The linear relationship between stress Xik applied to a piezoelectric material and resulting charge density Di is known as the direct piezoelectric effect and may be written as where dijk (C N−1) is a third-rank tensor of piezoelectric coefficients Piezoelectric effect  Another interesting property of piezoelectric material is they change their dimensions (contract or expand) when an electric field is applied to them. The converse piezoelectric effect describes the strain that is developed in a piezoelectric material due to the applied electric field: • where t denotes the transposed matrix. The units of the converse piezoelectric coefficient are (m V−1). DISCOVERY AND HISTROY Piezoelectric effect was first proven in 1880 by the French Physicist brothers Pierre and Jacques Curie. They combine their knowledge of Pyroelectric effect and the crystal structure of respective materials. Pyroelectric effect describes the generation of electric potential in response to temperature change. Among the materials showing Pyroelectricity, Quartz, Rochelle's salt, Tourmaline, Topaz shows the piezoelectricity most. Curies did not predict the converse or reverse piezoelectric effect. In 1881 Gabriel Lippmann mathematically deduced this concept and Curie brother confirmed it. CAUSE OF PIEZOELECTRICITY  Symmetric polar axis  Asymmetric polar axis 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. most of the dipoles are locked into a configuration of near alignment  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 Polarizing Piezoelectric Material Domain Wall Movement TYPES OF PIEZOELECTRIC MATERIAL Naturally occurring materials: Non-biological 1) 2) 3) 4) 5) 6) Quartz(SiO2) Berlinite (AlPO4) Sucrose (table sugar) Rochelle salt Topaz(Al2SiO4(F,OH)2) Tourmaline-group minerals 7) Lead titanate (PbTiO3) Biological material 1) 2) 3) 4) 5) 6) 7) Dry Bone Tendon Silk Wood Enamel Dentin DNA Synthetic materials B) Synthetic Ceramics 6) Barium titanate (BaTiO3) Lead zirconate titanate Potassium niobate (KNbO3) Lithium niobate (LiNbO3) Lithium tantalate (LiTaO3) Sodium tungstate 7) Zinc oxide (ZnO) 1) 2) 3) 4) 5) C) Lead-free Ceramics 1) 1) 2) 3) 4) Sodium potassium niobate ((K,Na)NbO3) Bismuth ferrite (BiFeO3) Sodium niobate (NaNbO3) Bismuth titanate(Bi4Ti3O12) Sodium bismuth titanate APPLICATION OF PIEZOELECTRICITY  1. As High Voltage Power Source:  Some piezoelectric substances like quartz can generate potential differences of thousand volts, during sufficient mechanical stress is applied. This high voltage pulse can be used to generate spark, micro scale energy harvesting, piezoelectric transformer. Following are some examples of uses-  LPG stove Lighter and Cigarette lighter Fig. 16 Fig. 17 2. Sensors and Actuators: Piezoelectric materials can be used to convert pressure, acceleration, temperature, strain or force direct to electrical emf. Hence the above parameters can be sensed or measured by means of such materials. Piezoelectric sensors are versatile tools for the measurement of various processes. They are used for quality assurance, process control and for research development in many industries. Generally after 1950 piezoelectric effect was started to be used as sensors and transducers. Some of the examples of piezo sensors are given belowHigh precision piezoelectric microphones Electric guitar pickup Piezoelectric micro balance (very sensitive chemical and biological sensors) Strain gauge An actuator is the mechanism by which a control system acts upon an environment. Actuator operated by a source of energy typically electric current, hydraulic fluid pressure or pneumatic pressure and converts that energy to motion. In piezoelectric actuators converse effect is used. By applying voltage the material changes its shape and this concept can be used to provide pressure in micro scale at very high precision than hydraulic and pneumatic pressure. We can use this technology to control operating of small nozzles (ink jet printer), micro scale movement Some examplesLoud speaker (voltage causes the vibration of piezoelectric polymer film) In high precision microscope for movement of lenses Inkjet printer (to drive the ejection of ink towards paper) Diesel engines (Fuel injector) X ray shutter Camera lens movement 3. As Frequency standard: Some piezoelectric crystals like quartz vibrate in a defined natural frequency when pulse is applied. As the result of vibration they provide reverse pulse. The mechanism can be used to mark the time and hence can be used as frequency standard. General quartz clock 4. Sonic and ultrasonic applications: By providing voltage pulse of high frequency to a piezoelectric material film it vibrates in frequency providing sonic and ultrasonic sound wave which can be used for Underwater submarine detection Ultrasound in medical technology Metal fault detection 5. Piezoelectric motor: Although piezoelectricity was a known concept “Ultrasonic piezoelectric motor” was a completely new concept during 21st century. Piezoelectric motors make use of the converse piezoelectric effect whereby the material produces acoustic or ultrasonic vibrations in order to produce a linear or rotary motion due to friction.. These motors are very small in size as shown in the figure FUTURE OUTLOOK  A. Power Generating Sidewalk The piezoelectric crystal arrays are arranged underneath pavements, sidewalks and other high traffic areas like highways, speed breakers for maximum voltage generation. The voltage thus generated from the array can be used to charge the chargeable Lithium batteries, capacitors etc. These batteries can be used as per the requirement. B. Railway Track We all must have seen the vibrating rails when train goes on it. This is one of the best examples of source of vibration. Hence there we can use the piezoelectric energy harvesting concept at stations. C. Power Generating Boots or Shoes In United States Defense Advance Research Project Agency (DARPA) initiated a innovative project on Energy harvesting which attempts to power battlefield equipment by piezoelectric generators embedded in soldiers' boots. However, these energy harvesting sources put an impact on the body. DARPA's effort to harness 1-2 watts from continuous shoe impact while walking were abandoned due to the discomfort from the additional energy expended by a person  D. Gyms and Workplaces Researchers are also working on the idea of utilizing the vibrations caused from the machines in the gym. At workplaces, while sitting on the chair, energy can be stored in the batteries by laying piezoelectric crystals in the chair. Also, the studies are being carried out to utilize the vibrations in a vehicle, like at clutches, gears, seats, shock-ups, foot rests. E. Mobile Keypad and Keyboards The piezoelectric crystals can be laid down under the keys of a mobile unit and keyboards. With the press of every key, the vibrations created can be used for piezoelectric crystal and hence can be used for charging purpose. Now smart phones are coming with touch screens but it can be applied to computer keyboards. F. Floor Mats, Tiles and Carpets A series of crystals can be laid below the floor mats, tiles and carpets which are frequently used at public places, dance clubs. When a bulk of people use this dance floor, enormous amount of voltage is generated which can be used to power the equipments of the night club. THANK YOU