Electrical and Electronics Engineering Materials

Electrical and Electronics Engineering Materials G.K. Banerjee

Electrical and Electronics Engineering Materials

Electrical and Electronics Engineering Materials G.K. Banerjee Professor and Head Department of Electrical Engineering School of Engineering and Technology (SET) IFTM University Moradabad Former Professor Department of Electrical Engineering College of Technology G.B. Pant University of Agriculture and Technology Pantnagar Delhi-110092 2015

ELECTRICAL AND ELECTRONICS ENGINEERING MATERIALS G.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.

Contents Preface xi 1. Atomic Structure 1 1.1 Introduction 1 1.2 The Quantum Number 3 1.3 The Hydrogen Atom 5 1.4 Nomenclature for Various Electronic States 9 1.5 The Electron Configuration of Atom 10 1.6 Molecules and General Bonding Principles 10 1.6.1 Bonding in Solids 10 1.6.2 Types of Bonding 12 1.6.3 Covalently Bonded Solids 15 1.6.4 Metallic Bonding 15 1.6.5 Ionic Bonding 16 1.6.6 Secondary Bonding 17 1.6.7 Mixed Bonding 18 1.7 Crystal System 19 1.7.1 Space Lattice 19 1.7.2 Lattice Parameter 19 1.8 Crystal Structure 20 1.8.1 Miller Indices 21 1.8.2 Crystal Symmetry 22 1.8.3 Bravais Lattice 22 1.9 Crystal Structure for Metallic Elements 22 1.9.1 Inter Planar Spacing 24 1.9.2 Coordination Number 25 1.9.3 Atomic Radius 26 1.9.4 Number of Atoms Per Unit Cell 27 1.9.5 Atomic Packing Factor 28 1.9.6 Volume, Planar and Linear Density of a Unit Cell 29 v

vi z Contents 1.10 Bragg s Law 32 1.11 Structural Imperfections 33 1.11.1 Point Defect 34 1.11.2 Line Defects 34 1.11.3 Surface Imperfections 34 1.12 Colour Centres 35 Review Questions 35 Numerical Problems 36 References 36 2. Dielectric Properties of Insulators in Static Fields 37 2.1 Introduction 37 2.2 Dielectric Parameters 38 2.2.1 Dielectric Constant 38 2.2.2 Dielectric Strength 38 2.2.3 Dielectric Loss 39 2.2.4 Dipole Moment 39 2.3 Polarisation 39 2.3.1 Polarizability 41 2.4 Mechanism of Polarisation 41 2.4.1 Electronic Polarisation 41 2.4.2 Ionic Polarisation 43 2.4.3 Orientational Polarisation 45 2.4.4 Interfacial Polarisation 49 2.5 The Internal Field in Solids and Liquids 51 2.6 The Static Dielectric Constant of Solids 53 2.6.1 Elemental Solid Dielectrics 54 2.6.2 Ionic Dielectrics without Permanent Dipoles 58 2.6.3 Polar Solids 58 2.7 Ferroelectric Materials and Their Properties 60 2.8 Spontaneous Polarisation 61 2.9 Classification of Ferroelectric Materials 63 2.10 Piezoelectric, Pyroelectric and Electrostrictive Materials 68 2.10.1 Piezoelectricity 68 2.10.2 Electromechanical Coupling Coefficient 70 Review Questions 78 Numerical Problems 79 References 79 3. Behaviour of Dielectric Materials in Alternating Field 80 3.1 Introduction 80 3.2 Frequency Dependence of the Electronic Polarisation 81 3.3 Frequency Dependence of Ionic Polarisation 86

Contents z vii 3.4 Complex Dielectric Constant of Non-polar Solids 87 3.5 Dipolar Relaxation 88 3.6 The Debye Equation 91 3.6.1 Cole-Cole Diagram 92 3.7 Dielectric Loss 94 3.7.1 The Equivalent Circuit 96 Review Questions 104 Numerical Problems 104 References 105 4. Insulating Materials and Their Applications 106 4.1 Introduction 106 4.1.1 Electrical Properties 107 4.1.2 Mechanical Properties 108 4.1.3 Thermal Properties 108 4.1.4 Chemical Properties 110 4.2 Classification of Insulating Materials 110 4.3 Paper and Pressboard 110 4.4 Fibrous Materials 111 4.4.1 Wood 111 4.4.2 Paper and Pressboard 111 4.4.3 Insulating Textiles 111 4.4.4 Inorganic Fibres 112 4.5 Impregnating, Coating, Filling and Bonding Materials 116 4.5.1 Waxes 116 4.5.2 Insulating Varnishes 116 4.5.3 Filling Compounds 117 4.5.4 Bonding Materials 117 4.5.5 Resins 117 4.6 Liquid Insulating Materials 119 4.6.1 Mineral Oils 119 4.6.2 Silicon Fluids 121 4.6.3 Fluorinated Liquids 121 4.6.4 Organic Ester Liquids 121 4.6.5 Vegetable Oils 122 4.6.6 Pyranol 122 4.6.7 Selection of Liquid Insulating Material 122 4.6.8 Application of Hydrogen and Mineral Oil in Electrical Machines 124 4.7 Dielectric Gases 124 4.7.1 Air 125 4.7.2 Nitrogen 125 4.7.3 Hydrogen 125 4.7.4 Oxide Gases 125

viii z Contents 4.7.5 Electronegative Gas 125 4.7.6 Vacuum as Dielectric 126 4.8 Composite Materials 126 4.9 Factors Effecting the Characteristics of Insulating Materials 127 4.9.1 Effect of Moisture on Insulation 127 4.9.2 Protection of Insulating Materials against Moisture 128 4.10 Insulating Materials Used in Electrical Equipment 129 4.11 Electronic Equipment 132 Review Questions 132 References 133 5. Magnetic Properties of Materials 134 5.1 Introduction 134 5.2 Fundamental Concepts Pertaining to Magnetic Fields 134 5.3 The Magnetic Dipole Moment of a Current Loop 137 5.4 The Magnetisation from a Macroscopic Point of View 138 5.5 Orbital Magnetic Dipole Moment and Angular Momentum of a Simple Atomic Model 141 5.6 Classification of Magnetic Materials 143 5.6.1 Diamagnetism 144 5.7 The Origin of Permanent Magnetic Dipole Moments 146 5.7.1 Orbital Magnetic Moments 146 5.7.2 Spin Magnetic Moments 147 5.7.3 Nuclear Magnetic Moments 148 5.8 Paramagnetism 148 5.9 Ferromagnetism 154 5.10 Spontaneous Magnetisation and Curie Weiss Law 157 5.10.1 Behaviour of Ferromagnetic Materials in High Temperature Region (T > T c ) 158 5.10.2 Behaviour of Ferromagnetic Materials below Curie Point (T < T c ) 159 5.11 Ferromagnetic Domains 160 5.12 Magnetic Anisotropy 163 5.13 Magnetostriction 163 5.14 Antiferromagnetism 164 5.15 Ferrimagnetic Materials (Ferrites) 168 5.15.1 Applications of Ferrimagnetic Materials 169 5.16 Magnetic Materials for Electrical Devices 170 5.16.1 Soft Magnetic Materials 171 5.16.2 Hard Magnetic Materials 172 5.17 Magnetic Resonance 174 Review Questions 178 Numerical Problems 179 References 180

Contents z ix 6. The Conductivity of Metals 181 6.1 Introduction 181 6.2 Atomic Interpretation of Ohm s Law 181 6.2.1 Mobility 184 6.3 Relaxation Time, Collision Time and Mean Free Path 184 6.3.1 Relaxation Time 184 6.3.2 Collision Time 185 6.3.3 Mean Free Path 186 6.4 Electron Scattering and Resistivity of Metals 188 6.5 Electrical Conductivity of Metallic Alloys 192 6.5.1 Linde s Rule 192 6.6 The Heat Developed in a Current-carrying Conductor (Joule s Law) 194 6.7 Thermal Conductivity of Metals Wiedemann Franz Law 195 6.8 Conductor Materials 199 6.8.1 High Conductivity Materials 200 6.8.2 High Resistivity Materials 201 6.8.3 Materials Used for Making Solder and Electrical Contacts 201 6.8.4 Non-metallic Conductors (Carbon Brushes) 202 6.8.5 Fusible Metals/Alloys (Fuses) 202 6.9 Superconductivity 203 6.9.1 Superconductivity The Free Electron Model 204 6.9.2 Thermodynamics of Superconductors 205 6.9.3 Properties of Superconductors 206 6.9.4 Meissner Effect 208 6.10 Classification of Superconductors 209 6.10.1 London Equation 212 6.10.2 High Temperature Superconductors 213 6.11 Superconducting Transmission Cables 215 Review Questions 221 Numerical Problems 222 References 223 7. Semiconductors 224 7.1 Introduction 224 7.2 The Chemical Bond in Germanium and Silicon 225 7.3 The Carrier Density in Intrinsic Semiconductors 227 7.3.1 The Conductivity of Intrinsic Semiconductors 230 7.4 The Extrinsic Semiconductor 231 7.5 The n-type Semiconductor 232 7.6 The p-type Semiconductors 233 7.7 Hall Effect in Semiconductors 234 7.8 Mechanism of Current Flow Drift and Diffusion Currents, The Einstein Relation 236

x z Contents 7.9 Materials for Fabrication of Semiconductor Devices 240 7.9.1 Passive Materials 241 7.9.2 Processing of Electronic Materials 244 7.10 Fabrication Technology 245 Review Questions 247 Numerical Problems 249 References 249 8. Junction Rectifiers and Transistors 250 8.1 Introduction 250 8.2 Minority and Majority Carrier Densities in Semiconductors 253 8.3 Drift Current and Diffusion Current 254 8.4 The Continuity Equation for Minority Carriers 256 8.5 The n-p Junction Rectifier 259 8.5.1 The Conduction Mechanism in n-p Junction Rectifier 262 8.6 The Capacitance of the Junction Barrier 265 8.7 The Junction Transistor 268 8.8 Thermistors and Variastors 271 8.8.1 Thermistors 271 8.8.2 Variastors 272 8.9 Silicon Controlled Rectifiers 272 8.9.1 Two Transistor Model 274 8.9.2 Thyristor Characteristics and Modes of Operation 275 8.9.3 Commutation of Thyristor 278 8.9.4 Heat Sinks and Mountings 279 Review Questions 280 Numerical Problems 281 References 281 9. Optical Properties of Materials 282 9.1 Introduction 282 9.2 The Electromagnetic Radiation Spectrum 284 9.2.1 Visible Radiation 285 9.3 Introduction to Optical Properties 285 9.3.1 Optical Properties in Materials 286 9.3.2 Refractive Index 288 9.3.3 Reflection 289 9.3.4 Birefringence 290 9.3.5 Translucency 290 9.3.6 Dispersion 291 9.3.7 Absorption 291 9.4 Colour Centres 293 9.5 Excitons 294

Contents z xi 9.6 Photoelectric Emission 294 9.7 Electroluminescence 296 9.8 Photoconductivity 296 9.9 Photoelectric Cells 297 9.9.1 Photoemissive Cell 297 9.9.2 Photoconductive Cells 297 9.9.3 Photovoltaic Cells 297 9.10 Lasers 298 9.10.1 Ruby Laser 301 9.10.2 Nd YAG Laser 302 9.10.3 Carbon Dioxide Laser 303 9.11 Optical Fibres 304 9.11.1 Structure of Optical Waveguide 304 9.11.2 Cut-off Parameters of Fibres 309 9.12 Fibre Materials 311 9.13 Latest Developments in Optical Fibres 311 9.13.1 Mechanism of Refractive Index Variation 315 9.14 Fabrication of Fibre 315 9.15 Fibre Cables 317 Review Questions 317 Numerical Problems 318 References 318 10. Materials for Direct Energy Conversion Devices 319 10.1 Introduction 319 10.2 Solar Cells 320 10.2.1 Equivalent Electrical Circuit of a Solar Cell 323 10.2.2 I-V and P-V Curves 324 10.3 Solar Thermal System 326 10.4 Fuel Cell 327 10.5 Magneto Hydro Dynamic Generators (MHD Generators) 328 10.6 Hydrogen Energy and Fuel Cell Technologies 329 10.6.1 Storage of Hydrogen 330 10.7 Thermoelectric Generators 330 10.8 Thermionic Converters 332 Review Questions 333 References 334 Index 335

Preface 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: gkb_1947@yahoo.co.in G.K. Banerjee xiii

Electrical And Electronics Engineering Materials 25% OFF Publisher : PHI Learning ISBN : 9788120350144 Author : GK Banerjee Type the URL : http://www.kopykitab.com/product/10351 Get this ebook