Electrical and Electronics Engineering Materials

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1 Electrical and Electronics Engineering Materials G.K. Banerjee

2 Electrical and Electronics Engineering Materials

4 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

5 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 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 and Printed by Mudrak, 30-A, Patparganj, Delhi

6 Contents Preface xi 1. Atomic Structure Introduction The Quantum Number The Hydrogen Atom Nomenclature for Various Electronic States The Electron Configuration of Atom Molecules and General Bonding Principles Bonding in Solids Types of Bonding Covalently Bonded Solids Metallic Bonding Ionic Bonding Secondary Bonding Mixed Bonding Crystal System Space Lattice Lattice Parameter Crystal Structure Miller Indices Crystal Symmetry Bravais Lattice Crystal Structure for Metallic Elements Inter Planar Spacing Coordination Number Atomic Radius Number of Atoms Per Unit Cell Atomic Packing Factor Volume, Planar and Linear Density of a Unit Cell 29 v

7 vi z Contents 1.10 Bragg s Law Structural Imperfections Point Defect Line Defects Surface Imperfections Colour Centres 35 Review Questions 35 Numerical Problems 36 References Dielectric Properties of Insulators in Static Fields Introduction Dielectric Parameters Dielectric Constant Dielectric Strength Dielectric Loss Dipole Moment Polarisation Polarizability Mechanism of Polarisation Electronic Polarisation Ionic Polarisation Orientational Polarisation Interfacial Polarisation The Internal Field in Solids and Liquids The Static Dielectric Constant of Solids Elemental Solid Dielectrics Ionic Dielectrics without Permanent Dipoles Polar Solids Ferroelectric Materials and Their Properties Spontaneous Polarisation Classification of Ferroelectric Materials Piezoelectric, Pyroelectric and Electrostrictive Materials Piezoelectricity Electromechanical Coupling Coefficient 70 Review Questions 78 Numerical Problems 79 References Behaviour of Dielectric Materials in Alternating Field Introduction Frequency Dependence of the Electronic Polarisation Frequency Dependence of Ionic Polarisation 86

8 Contents z vii 3.4 Complex Dielectric Constant of Non-polar Solids Dipolar Relaxation The Debye Equation Cole-Cole Diagram Dielectric Loss The Equivalent Circuit 96 Review Questions 104 Numerical Problems 104 References Insulating Materials and Their Applications Introduction Electrical Properties Mechanical Properties Thermal Properties Chemical Properties Classification of Insulating Materials Paper and Pressboard Fibrous Materials Wood Paper and Pressboard Insulating Textiles Inorganic Fibres Impregnating, Coating, Filling and Bonding Materials Waxes Insulating Varnishes Filling Compounds Bonding Materials Resins Liquid Insulating Materials Mineral Oils Silicon Fluids Fluorinated Liquids Organic Ester Liquids Vegetable Oils Pyranol Selection of Liquid Insulating Material Application of Hydrogen and Mineral Oil in Electrical Machines Dielectric Gases Air Nitrogen Hydrogen Oxide Gases 125

9 viii z Contents Electronegative Gas Vacuum as Dielectric Composite Materials Factors Effecting the Characteristics of Insulating Materials Effect of Moisture on Insulation Protection of Insulating Materials against Moisture Insulating Materials Used in Electrical Equipment Electronic Equipment 132 Review Questions 132 References Magnetic Properties of Materials Introduction Fundamental Concepts Pertaining to Magnetic Fields The Magnetic Dipole Moment of a Current Loop The Magnetisation from a Macroscopic Point of View Orbital Magnetic Dipole Moment and Angular Momentum of a Simple Atomic Model Classification of Magnetic Materials Diamagnetism The Origin of Permanent Magnetic Dipole Moments Orbital Magnetic Moments Spin Magnetic Moments Nuclear Magnetic Moments Paramagnetism Ferromagnetism Spontaneous Magnetisation and Curie Weiss Law Behaviour of Ferromagnetic Materials in High Temperature Region (T > T c ) Behaviour of Ferromagnetic Materials below Curie Point (T < T c ) Ferromagnetic Domains Magnetic Anisotropy Magnetostriction Antiferromagnetism Ferrimagnetic Materials (Ferrites) Applications of Ferrimagnetic Materials Magnetic Materials for Electrical Devices Soft Magnetic Materials Hard Magnetic Materials Magnetic Resonance 174 Review Questions 178 Numerical Problems 179 References 180

10 Contents z ix 6. The Conductivity of Metals Introduction Atomic Interpretation of Ohm s Law Mobility Relaxation Time, Collision Time and Mean Free Path Relaxation Time Collision Time Mean Free Path Electron Scattering and Resistivity of Metals Electrical Conductivity of Metallic Alloys Linde s Rule The Heat Developed in a Current-carrying Conductor (Joule s Law) Thermal Conductivity of Metals Wiedemann Franz Law Conductor Materials High Conductivity Materials High Resistivity Materials Materials Used for Making Solder and Electrical Contacts Non-metallic Conductors (Carbon Brushes) Fusible Metals/Alloys (Fuses) Superconductivity Superconductivity The Free Electron Model Thermodynamics of Superconductors Properties of Superconductors Meissner Effect Classification of Superconductors London Equation High Temperature Superconductors Superconducting Transmission Cables 215 Review Questions 221 Numerical Problems 222 References Semiconductors Introduction The Chemical Bond in Germanium and Silicon The Carrier Density in Intrinsic Semiconductors The Conductivity of Intrinsic Semiconductors The Extrinsic Semiconductor The n-type Semiconductor The p-type Semiconductors Hall Effect in Semiconductors Mechanism of Current Flow Drift and Diffusion Currents, The Einstein Relation 236

11 x z Contents 7.9 Materials for Fabrication of Semiconductor Devices Passive Materials Processing of Electronic Materials Fabrication Technology 245 Review Questions 247 Numerical Problems 249 References Junction Rectifiers and Transistors Introduction Minority and Majority Carrier Densities in Semiconductors Drift Current and Diffusion Current The Continuity Equation for Minority Carriers The n-p Junction Rectifier The Conduction Mechanism in n-p Junction Rectifier The Capacitance of the Junction Barrier The Junction Transistor Thermistors and Variastors Thermistors Variastors Silicon Controlled Rectifiers Two Transistor Model Thyristor Characteristics and Modes of Operation Commutation of Thyristor Heat Sinks and Mountings 279 Review Questions 280 Numerical Problems 281 References Optical Properties of Materials Introduction The Electromagnetic Radiation Spectrum Visible Radiation Introduction to Optical Properties Optical Properties in Materials Refractive Index Reflection Birefringence Translucency Dispersion Absorption Colour Centres Excitons 294

12 Contents z xi 9.6 Photoelectric Emission Electroluminescence Photoconductivity Photoelectric Cells Photoemissive Cell Photoconductive Cells Photovoltaic Cells Lasers Ruby Laser Nd YAG Laser Carbon Dioxide Laser Optical Fibres Structure of Optical Waveguide Cut-off Parameters of Fibres Fibre Materials Latest Developments in Optical Fibres Mechanism of Refractive Index Variation Fabrication of Fibre Fibre Cables 317 Review Questions 317 Numerical Problems 318 References Materials for Direct Energy Conversion Devices Introduction Solar Cells Equivalent Electrical Circuit of a Solar Cell I-V and P-V Curves Solar Thermal System Fuel Cell Magneto Hydro Dynamic Generators (MHD Generators) Hydrogen Energy and Fuel Cell Technologies Storage of Hydrogen Thermoelectric Generators Thermionic Converters 332 Review Questions 333 References 334 Index 335

14 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

: 9788120350144 Author : GK Banerjee Type the

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SOLID STATE PHYSICS. Second Edition. John Wiley & Sons. J. R. Hook H. E. Hall. Department of Physics, University of Manchester

SOLID STATE PHYSICS. Second Edition. John Wiley & Sons. J. R. Hook H. E. Hall. Department of Physics, University of Manchester SOLID STATE PHYSICS Second Edition J. R. Hook H. E. Hall Department of Physics, University of Manchester John Wiley & Sons CHICHESTER NEW YORK BRISBANE TORONTO SINGAPORE Contents Flow diagram Inside front