Electrical and Electronics Engineering Materials

G.K. Banerjee

Electricaland Electronics EngineeringMaterials

Electrical and Electronics Engineering Materials

Electrical and Electronics Engineering Materials

G.K. BanerjeeProfessor and Head

Department of Electrical EngineeringSchool of Engineering and Technology (SET)

IFTM UniversityMoradabad

Former ProfessorDepartment of Electrical Engineering

College of TechnologyG.B. Pant University of Agriculture and Technology

Pantnagar

Delhi-1100922015

ELECTRICAL AND ELECTRONICS ENGINEERING MATERIALSG.K. Banerjee

© 2015 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher.

ISBN-978-81-203-5014-4

The export rights of this book are vested solely with the publisher.

Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111, Patparganj Industrial Estate, Delhi-110092 and Printed by Mudrak, 30-A, Patparganj, Delhi-110091.

Preface xi

1. Atomic Structure 11.1 Introduction 11.2 The Quantum Number 31.3 The Hydrogen Atom 51.4 Nomenclature for Various Electronic States 91.5 The Electron Configuration of Atom 101.6 Molecules and General Bonding Principles 10

1.6.1 Bonding in Solids 101.6.2 Types of Bonding 121.6.3 Covalently Bonded Solids 151.6.4 Metallic Bonding 151.6.5 Ionic Bonding 161.6.6 Secondary Bonding 171.6.7 Mixed Bonding 18

1.7 Crystal System 191.7.1 Space Lattice 191.7.2 Lattice Parameter 19

1.8 Crystal Structure 201.8.1 Miller Indices 211.8.2 Crystal Symmetry 221.8.3 Bravais Lattice 22

1.9 Crystal Structure for Metallic Elements 221.9.1 Inter Planar Spacing 241.9.2 Coordination Number 251.9.3 Atomic Radius 261.9.4 Number of Atoms Per Unit Cell 271.9.5 Atomic Packing Factor 281.9.6 Volume, Planar and Linear Density of a Unit Cell 29

v

Contents

vi z Contents

1.10 Bragg’s Law 321.11 Structural Imperfections 33

1.11.1 Point Defect 341.11.2 Line Defects 341.11.3 Surface Imperfections 34

1.12 Colour Centres 35

Review Questions 35Numerical Problems 36References 36

2. Dielectric Properties of Insulators in Static Fields 372.1 Introduction 372.2 Dielectric Parameters 38

2.2.1 Dielectric Constant 382.2.2 Dielectric Strength 382.2.3 Dielectric Loss 392.2.4 Dipole Moment 39

2.3 Polarisation 392.3.1 Polarizability 41

2.4 Mechanism of Polarisation 412.4.1 Electronic Polarisation 412.4.2 Ionic Polarisation 432.4.3 Orientational Polarisation 452.4.4 Interfacial Polarisation 49

2.5 The Internal Field in Solids and Liquids 512.6 The Static Dielectric Constant of Solids 53

2.6.1 Elemental Solid Dielectrics 542.6.2 Ionic Dielectrics without Permanent Dipoles 582.6.3 Polar Solids 58

2.7 Ferroelectric Materials and Their Properties 602.8 Spontaneous Polarisation 612.9 Classification of Ferroelectric Materials 632.10 Piezoelectric, Pyroelectric and Electrostrictive Materials 68

2.10.1 Piezoelectricity 682.10.2 Electromechanical Coupling Coefficient 70


3. Behaviour of Dielectric Materials in Alternating Field 803.1 Introduction 803.2 Frequency Dependence of the Electronic Polarisation 813.3 Frequency Dependence of Ionic Polarisation 86

Contents z vii

3.4 Complex Dielectric Constant of Non-polar Solids 873.5 Dipolar Relaxation 883.6 The Debye Equation 91

3.6.1 Cole-Cole Diagram 923.7 Dielectric Loss 94

3.7.1 The Equivalent Circuit 96

Review Questions 104

Numerical Problems 104

References 105

4. Insulating Materials and Their Applications 1064.1 Introduction 106

4.1.1 Electrical Properties 1074.1.2 Mechanical Properties 1084.1.3 Thermal Properties 1084.1.4 Chemical Properties 110

4.2 Classification of Insulating Materials 1104.3 Paper and Pressboard 1104.4 Fibrous Materials 111

4.4.1 Wood 1114.4.2 Paper and Pressboard 1114.4.3 Insulating Textiles 1114.4.4 Inorganic Fibres 112

4.5 Impregnating, Coating, Filling and Bonding Materials 1164.5.1 Waxes 1164.5.2 Insulating Varnishes 1164.5.3 Filling Compounds 1174.5.4 Bonding Materials 1174.5.5 Resins 117

4.6 Liquid Insulating Materials 1194.6.1 Mineral Oils 1194.6.2 Silicon Fluids 1214.6.3 Fluorinated Liquids 1214.6.4 Organic Ester Liquids 1214.6.5 Vegetable Oils 1224.6.6 Pyranol 1224.6.7 Selection of Liquid Insulating Material 1224.6.8 Application of Hydrogen and Mineral Oil in Electrical Machines 124

4.7 Dielectric Gases 1244.7.1 Air 1254.7.2 Nitrogen 1254.7.3 Hydrogen 1254.7.4 Oxide Gases 125

viii z Contents

4.7.5 Electronegative Gas 1254.7.6 Vacuum as Dielectric 126

4.8 Composite Materials 1264.9 Factors Effecting the Characteristics of Insulating Materials 127

4.9.1 Effect of Moisture on Insulation 1274.9.2 Protection of Insulating Materials against Moisture 128

4.10 Insulating Materials Used in Electrical Equipment 1294.11 Electronic Equipment 132

Review Questions 132References 133

5. Magnetic Properties of Materials 1345.1 Introduction 1345.2 Fundamental Concepts Pertaining to Magnetic Fields 1345.3 The Magnetic Dipole Moment of a Current Loop 1375.4 The Magnetisation from a Macroscopic Point of View 1385.5 Orbital Magnetic Dipole Moment and Angular Momentum of

a Simple Atomic Model 1415.6 Classification of Magnetic Materials 143

5.6.1 Diamagnetism 1445.7 The Origin of Permanent Magnetic Dipole Moments 146

5.7.1 Orbital Magnetic Moments 1465.7.2 Spin Magnetic Moments 1475.7.3 Nuclear Magnetic Moments 148

5.8 Paramagnetism 1485.9 Ferromagnetism 1545.10 Spontaneous Magnetisation and Curie–Weiss Law 157

5.10.1 Behaviour of Ferromagnetic Materials in High Temperature Region (T > Tc) 158

5.10.2 Behaviour of Ferromagnetic Materials below Curie Point (T < Tc) 159

5.11 Ferromagnetic Domains 1605.12 Magnetic Anisotropy 1635.13 Magnetostriction 1635.14 Antiferromagnetism 1645.15 Ferrimagnetic Materials (Ferrites) 168

5.15.1 Applications of Ferrimagnetic Materials 1695.16 Magnetic Materials for Electrical Devices 170

5.16.1 Soft Magnetic Materials 1715.16.2 Hard Magnetic Materials 172

5.17 Magnetic Resonance 174


Contents z ix

6. The Conductivity of Metals 1816.1 Introduction 1816.2 Atomic Interpretation of Ohm’s Law 181

6.2.1 Mobility 1846.3 Relaxation Time, Collision Time and Mean Free Path 184

6.3.1 Relaxation Time 1846.3.2 Collision Time 1856.3.3 Mean Free Path 186

6.4 Electron Scattering and Resistivity of Metals 1886.5 Electrical Conductivity of Metallic Alloys 192

6.5.1 Linde’s Rule 1926.6 The Heat Developed in a Current-carrying Conductor (Joule’s Law) 1946.7 Thermal Conductivity of Metals—Wiedemann Franz Law 1956.8 Conductor Materials 199

6.8.1 High Conductivity Materials 2006.8.2 High Resistivity Materials 2016.8.3 Materials Used for Making Solder and Electrical Contacts 2016.8.4 Non-metallic Conductors (Carbon Brushes) 2026.8.5 Fusible Metals/Alloys (Fuses) 202

6.9 Superconductivity 2036.9.1 Superconductivity—The Free Electron Model 2046.9.2 Thermodynamics of Superconductors 2056.9.3 Properties of Superconductors 2066.9.4 Meissner Effect 208

6.10 Classification of Superconductors 2096.10.1 London Equation 2126.10.2 High Temperature Superconductors 213

6.11 Superconducting Transmission Cables 215


7. Semiconductors 2247.1 Introduction 2247.2 The Chemical Bond in Germanium and Silicon 2257.3 The Carrier Density in Intrinsic Semiconductors 227

7.3.1 The Conductivity of Intrinsic Semiconductors 2307.4 The Extrinsic Semiconductor 2317.5 The n-type Semiconductor 2327.6 The p-type Semiconductors 2337.7 Hall Effect in Semiconductors 2347.8 Mechanism of Current Flow—Drift and Diffusion Currents, The Einstein

Relation 236

x z Contents

7.9 Materials for Fabrication of Semiconductor Devices 2407.9.1 Passive Materials 2417.9.2 Processing of Electronic Materials 244

7.10 Fabrication Technology 245


8. Junction Rectifiers and Transistors 2508.1 Introduction 2508.2 Minority and Majority Carrier Densities in Semiconductors 2538.3 Drift Current and Diffusion Current 2548.4 The Continuity Equation for Minority Carriers 2568.5 The n-p Junction Rectifier 259

8.5.1 The Conduction Mechanism in n-p Junction Rectifier 2628.6 The Capacitance of the Junction Barrier 2658.7 The Junction Transistor 2688.8 Thermistors and Variastors 271

8.8.1 Thermistors 2718.8.2 Variastors 272

8.9 Silicon Controlled Rectifiers 2728.9.1 Two Transistor Model 2748.9.2 Thyristor Characteristics and Modes of Operation 2758.9.3 Commutation of Thyristor 2788.9.4 Heat Sinks and Mountings 279


9. Optical Properties of Materials 2829.1 Introduction 2829.2 The Electromagnetic Radiation Spectrum 284

9.2.1 Visible Radiation 2859.3 Introduction to Optical Properties 285

9.3.1 Optical Properties in Materials 2869.3.2 Refractive Index 2889.3.3 Reflection 2899.3.4 Birefringence 2909.3.5 Translucency 2909.3.6 Dispersion 2919.3.7 Absorption 291

9.4 Colour Centres 2939.5 Excitons 294

Contents z xi

9.6 Photoelectric Emission 2949.7 Electroluminescence 2969.8 Photoconductivity 2969.9 Photoelectric Cells 297

9.9.1 Photoemissive Cell 2979.9.2 Photoconductive Cells 2979.9.3 Photovoltaic Cells 297

9.10 Lasers 2989.10.1 Ruby Laser 3019.10.2 Nd–YAG Laser 3029.10.3 Carbon Dioxide Laser 303

9.11 Optical Fibres 3049.11.1 Structure of Optical Waveguide 3049.11.2 Cut-off Parameters of Fibres 309

9.12 Fibre Materials 3119.13 Latest Developments in Optical Fibres 311

9.13.1 Mechanism of Refractive Index Variation 3159.14 Fabrication of Fibre 3159.15 Fibre Cables 317

Review Questions 317

Numerical Problems 318

References 318

10. Materials for Direct Energy Conversion Devices 31910.1 Introduction 31910.2 Solar Cells 320

10.2.1 Equivalent Electrical Circuit of a Solar Cell 32310.2.2 I-V and P-V Curves 324

10.3 Solar Thermal System 32610.4 Fuel Cell 32710.5 Magneto Hydro Dynamic Generators (MHD Generators) 32810.6 Hydrogen Energy and Fuel Cell Technologies 329

10.6.1 Storage of Hydrogen 33010.7 Thermoelectric Generators 33010.8 Thermionic Converters 332

Review Questions 333References 334

Index 335

In modern electrical industries, solutions to various problems require a thorough knowledge of the fundamental principles of material science. Thus, it has now becomes a discipline in its own right and it incorporates the basic principles of physics, chemistry and engineering. The increasing importance of material science has introduced a number of new devices in electrical engineering. Therefore, a course in material science is now considered an essential requirement in almost all the disciplines of engineering at undergraduate level.

This book contains ten chapters. The first chapter gives an introduction to atomic structure and some basic concepts of material science. In the next two chapters, the behaviour of dielectrics (insulating materials) and their properties under the influence of DC and AC fields have been discussed. Chapter 4 covers the properties and applications of some of the important insulating materials such as gases, liquids and solids. In Chapter 5, the theory of magnetic materials and their applications as soft and hard materials have been discussed. Chapter 6 deals with the properties of the conducting and superconducting materials. Chapters 7 and 8 deal with the theory of semiconducting materials, junction transistors and rectifiers. Optical properties of various types of materials have been covered in Chapter 9. Chapter 10 is a small chapter in which introduction to direct energy conversion devices has been given and their material problems have been discussed.

Each chapter has been written in a lucid and systemic manner with necessary mathematical derivations, illustrations, examples and tutorial problems. A set of review questions has been included at the end of each chapter. In some of the chapters, where required, a set of numerical problems also included. In collecting the information on the subject, various books on material science, solid state physics and technical papers have been consulted and a list of references has been given at the end of each chapter.

Thanks to those who helped me directly or indirectly to complete this book. My special thanks goes to PHI Learning for publishing this book on time.

The author will welcome any suggestion and correction for the improvement of the book. Readers may give their suggestions and corrections at: [email protected]

G.K. Banerjee

xiii

Preface

Electrical And Electronics EngineeringMaterials

Publisher : PHI Learning ISBN : 9788120350144 Author : GK Banerjee

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Electrical and Electronics Engineering Materials