dielectric classification and microwave applications

1. By E SIVANAGI REDDY
12ACPA02
ACRHEM

3.  Introduction
 Dielectric Materials
 Classification of Dielectrics
 Applications of Dielectrics
 Microwaves
 Applications of Microwaves
 Risk of risk Research
 Microwave Dielectrics
 Summary and Conclusion

4.  Dielectric is a material that permits the passage of
electric field or flux
Eg : Rubber, glass, waxed paper
 Dielectrics are insulating materials that exhibit the
property of electrical polarization
 No ideal dielectric in the planet.

5.  Bulk Single crystals
 Polycrystals
 Ceramics
 Thin films
 Polymers
 Nano dielectrics
 rubber

6.  Good Mechanical and Chemical Stability
 Minimum number of defects and impurities
 Large forbidden band gap
 Amorphous Structure
 Small reaction to physical change
i.e, low aging and temperature behavior
 Lack of sensitivity to moisture
 No pin holes or weak points that have to be “burnt out”.
Lenon I.Missel, R.Glang (Ed.)
Hand Book of Thin film Technology
McGraw-Hill Book Company

7.  A dielectric is an electrical insulator that can be polarized by
an applied electric field.
 The polarization of a region is defined as the dipole moment
per unit volume
 The relation between electronic polarization to dielectric
constant is
2
1 4 n 1 4 e
N (CGS ) Nk
2 3 2 k
n 2 3 k
Clausius- Mossotti equation
At high frequency =n2
n= refractive index
α= electronic polarisability

8. Microwaves and Metals
By Manoj Gupta, Eugene Wong Wai Leong

9.  A dielectric material is made up of atoms or
molecules that possess electric polarization
basing on it they are classified as
 Linear dielectric materials
I. Non Polar dielectrics (E)
II. polar dielectrics(E+I)
III. Dipolar dielectrics (E+I+O)
 Non linear dielectrics(spontaneous polarization )
• absence of a center of symmetry

10. Fig. Classification of crystals showing the classes with
piezoelectric, Pyroelectric and Ferro electric

11. Ability of certain crystals to generate a
voltage in response to applied
mechanical stress.
Quartz Silica ( SiO2) –repeated Strecture
(but not ferroelectric)
Piezoelectric effect
The potential created in certain
materials when they are heated
Pyroelectric effect Lithium tantalate LiTaO3
The phenomenon whereby certain ionic
crystals may exhibit a spontaneous
dipole moment.
Lithium niobateLiNbO3
Ferroelectric effect

12. N.IZYUMSKAYA et. al Critical Reviews in Solid State and
Materials Sciences,34:89–179,2009

13.  D.C is a measure of the extent to which the
electrical charge distribution in the material can be
distorted or polarized by the application of electric
field.
 Dielectric constant depend on
1. Frequency of applied electric field
2. Chemical structure
3. Imperfections
4. Temperature and pressure of
material
Do IT PoMS
University of Cambridge

14. Dielectric constants and Strengths for Some
Dielectric Materials
William D. Callister, Jr.
Materials Science and Engineering
An Introduction

15. Sensors
Arthur Von Hippel (Ed.)
Dielectric Materials and Applications
Artech House ,London (1995)

17. Mailadil ,T. Sebastian
Dielectric Materials for Wireless Communication

19.  Electromagnetic Spectrum MW have wavelengths 1mm -
1m , frequencies of 0.3 - 300 GHz.
 To avoid interference with telecommunication, cellular
phones and radar, by International convention most
domestic and commercial MW heating operate wavelength
of 12.2 cm, 2.45 GHz.
 MW can be divided in an electric field and a magnetic
field component and the former is responsible for heating.
 MW is generated by vacuum tubes, magnetron, multimode
or mono-mode Commercial ovens

20. Interaction of the Electromagnetic field Frequency dependence of the polarization
with materials mechanism for dielectrics
Microwaves and Metals
By Manoj Gupta, Eugene Wong Wai
Leong

21.  Microwave heating
 Communications
 Industrials
 Power transmissions
 Medical
 Scientific
 Rader detection
 Weather control
Microwaves and Metals
By Manoj Gupta, Eugene Wong Wai
Leong

22. APPLICATIONS OF MICROWAVES
Blackout Bomb: Air Force's High-
Powered Microwave Weapons Fry
Enemy Equipment
Active Denial System (ADS)

23. ISRO

25. Dielectric resonators

26.  Dielectrics are the materials having perment electric dipole
moment .
 Different type of dielectrics(Piezo, Ferro, Pyro electrics) have
Potential applications in various fields.
 Microwaves form part of the EM spectrum, with frequency
ranging from 300MHz to 300GHz.
 Microwave usage is extremely diverse, with applications in
heating, radar, communication, industry, Science, medicine
and power transmission.

27.  1.Gupta,Wong : Microwaves and Metals
John Wiley & Sons (Asia)Pt Ltd, 2007
 2. Kenji Uchino :Ferroelectric Devices 2/e
CRC Press ,2010
 3. Kwan Chi Kao :Dielectric Phenomena in Solids
Elsevier Academic Press,2004
 4. Charles Kittel: Introduction to Solid State Physics 7/e
WILEY-INDIA,2007
 5. Arthur Von Hipple(Ed.): Dielectric Materials and waves
Artech House, London ,1995