X-Ray Fluorescence Spectrometry E-Book

Ron Jenkins

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Chemical Analysis: A Series of Monographs on Analytical Chemistry and Its Applications
• Sprache: Englisch

Seitenzahl: 337

Veröffentlichungsjahr: 2012

Beschreibung

X-ray fluorescence spectroscopy, one of the most powerful and flexible techniques available for the analysis and characterization of materials today, has gone through major changes during the past decade. Fully revised and expanded by 30%, X-Ray Fluorescence Spectrometry, Second Edition incorporates the latest industrial and scientific trends in all areas. It updates all previous material and adds new chapters on such topics as the history of X-ray fluorescence spectroscopy, the design of X-ray spectrometers, state-of-the-art applications, and X-ray spectra. Ron Jenkins draws on his extensive experience in training and consulting industry professionals for this clear and concise treatment, covering first the basic aspects of X rays, then the methodology of X-ray fluorescence spectroscopy and available instrumentation. He offers a comparison between wavelength and energy dispersive spectrometers as well as step-by-step guidelines to X-ray spectrometric techniques for qualitative and quantitative analysis-from specimen preparation to real-world industrial application. Favored by the American Chemical Society and the International Centre for Diffraction Data, X-Ray Fluorescence Spectrometry, Second Edition is an ideal introduction for newcomers to the field and an invaluable reference for experienced spectroscopists-in chemical analysis, geology, metallurgy, and materials science. An up-to-date review of X-ray spectroscopic techniques. This proven guidebook for industry professionals is thoroughly updated and expanded to reflect advances in X-ray analysis over the last decade. X-Ray Fluorescence Spectrometry, Second Edition includes: * The history of X-ray fluorescence spectrometry-new to this edition. * A critical review of the most useful X-ray spectrometers. * Techniques and procedures for quantitative and qualitative analysis. * Modern applications and industrial trends. * X-ray spectra-new to this edition.

Leseprobe

CONTENTS

Cover

Half Title page

Title page

Copyright page

Preface to the First Edition

Preface to the Second Edition

Cumulative Listing of Volumes in Series

Chapter 1: Production and Properties X-Rays

1.1. Introduction

1.2. Continuous Radiation

1.3. Characteristic Radiation

1.4. Absorption of X-Rays

1.5. Coherent and Incoherent Scattering

1.6. Interference and Diffraction

Bibliography

Chapter 2: Industrial Applications of X-Rays

2.1. Introduction

2.2. Diagnostic Uses of X-Rays

2.3. Tomography

2.4. Level and Thickness Gauging

2.5. X-Ray Thickness Gauging

2.6. Nondestructive Testing

2.7. Security Screening Systems

2.8. X-Ray Lithography

2.9. X-Ray Astronomy

Bibliography

Chapter 3: X-Ray Diffraction

3.1. Use of X-Ray Diffraction to Study the Crystalline State

3.2. The Powder Method

3.3. Use of X-Ray Powder Cameras

3.4. The Powder Diffractometer

3.5. Qualitative Applications of the X-Ray Powder Method

3.6. Quantitative Methods in X-Ray Powder Diffraction

3.7. Other Applications of X-Ray Diffraction

Bibliography

Chapter 4: X-Ray Spectra

4.1. Introduction

4.2. Electron Configuration of the Elements

4.3. Fluorescent Yield

4.4. Relationship Between Wavelength and Atomic Number

4.5. Normal Transitions (Diagram Lines)

4.6. Satellite Lines

4.7. Characteristic Line Spectra

4.8. K Spectra

4.9. L Spectra

4.10. M Spectra

Bibliography

Chapter 5: History and Development of X-Ray Fluorescence Spectrometry

5.1. Historical Development of X-Ray Spectrometry

5.2. Early Ideas About X-Ray Fluorescence

5.3. Rebirth of X-Ray Fluorescence

5.4. Evolution of Hardware Control Methods

5.5. The Growing Role of X-Ray Fluorescence Analysis in Industry and Research

5.6. The Arrival of Energy Dispersive Spectrometry

5.7. Evolution of Mathematical Correction Procedures

5.8. X-Ray Analysis in the 1970s

5.9. More Recent Development of X-Ray Fluorescence

Bibliography

Chapter 6: Instrumentation for X-Ray Spectrometry

6.1. Introduction

6.2. Excitation of X-Rays

6.3. Detection of X-Rays

6.4. Wavelength Dispersive Spectrometers

6.5. Energy Dispersive Spectrometers

Bibliography

Chapter 7: Comparison of Wavelength and Energy Dispersive Spectrometers

7.1. Introduction

7.2. The Measurable Atomic Number Range

7.3. The Resolution of Lines

7.4. Measurement of Low Concentrations

7.5. Qualitative Analysis

7.6. Geometric Constraints of Wavelength and Energy Dispersive Spectrometers

Bibliography

Chapter 8: More Recent Trends in X-Ray Fluorescence Instrumentation

8.1. The Role of X-Ray Fluorescence in Industry and Research

8.2. Scope of the X-Ray Fluorescence Method

8.3. The Determination of Low Atomic Number Elements

8.4. Total Reflection X-Ray Fluorescence

8.5. Synchrotron Source X-Ray Fluorescence—SSXRF

8.6. Proton Induced X-Ray Fluorescence

Bibliography

Chapter 9: Specimen Preparation and Presentation

9.1. Form of The Sample for X-Ray Analysis

9.2. Direct Analysis of Solid Samples

9.3. Preparation of Powder Samples

9.4. Direct Analysis of Solutions

9.5. Analysis of Small Amounts of Sample

9.6. Preconcentration Techniques

Bibliography

Chapter 10: Use of X-Ray Spectrometry for Qualitative Analysis

10.1. Introduction to Qualitative Analysis

10.2. Relative Intensities of X-Ray Lines

10.3. Qualitative Interpretation of X-Ray Spectrograms

10.4. Semiquantitative Analysis

Bibliography

Chapter 11: Considerations in Quantitative X-Ray Fluorescence Analysis

11.1. Conversion of Characteristic Line Intensity to Analyte Concentration

11.2. Influence of the Background

11.3. Statistical Counting Errors

11.4. Matrix Effects

11.5. Analysis of Low Concentrations

Bibliography

Chapter 12: Quantitative Procedures in X-Ray Fluorescence Analysis

12.1. Overview of Quantitative Methods

12.2. Measurement of Pure Intensities

12.3. Single Element Methods

12.4. Multiple Element Methods

Bibliography

Chapter 13: Applications of X-Ray Methods

13.1. Comparison of X-Ray Fluorescence with Other Instrumental Methods

13.2. Application of X-Ray Spectrometry

13.3. Combined Diffraction and Fluorescence Techniques

13.4. Portable XRF Equipment

13.5. On-Stream Analysis

Bibliography

Index

X-Ray Fluorescence Spectrometry

Copyright © 1999 by John Wiley & Sons, Inc.

All rights reserved.

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, [phone], fax [phone]. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, [phone], fax [phone], E-Mail: [email protected].

Library of Congress Cataloging-in-Publication Data:

Jenkins, Ron, 1932-X-ray fluorescence spectrometry / Ron Jenkins. — 2nd ed.p. cm. — (Chemical analysis ; v. 152)“A Wiley-Interscience publication.”Includes bibliographical references and index.ISBN 0-471-29942-1 (cloth : alk. paper)1. X-ray spectroscopy. 2. Fluorescence spectroscopy. I. Title. II. series.QD96.X2J47   1999543’.08586—dc2198-39008

PREFACE TO THE FIRST EDITION

PREFACE TO THE SECOND EDITION

I was gratified to learn that the first edition of this book found a place in the teaching of X-Ray Fluorescence Spectrometry. Both the American Chemical Society, and the International Centre for Diffraction Data, have, for a number of years, used the book as a course text in their X-ray fluorescence schools.

In preparing a second edition, I have taken the advantage in expanding the text to give more extensive coverage. In addition to a complete review and update of each chapter, new chapters have been added on “X-Ray Spectra” and “History and Development.” The text is now about 30% larger than the first edition. I am grateful to those who have contributed to this work and am especially indebted to Dr. Sue Quick and Don Desrosiers for their painstaking work in proofing the manuscript.

Newtown Square, PA

RON JENKINS

CHEMICAL ANALYSIS

A SERIES OF MONOGRAPHS ON ANALYTICAL CHEMISTRY AND ITS APPLICATIONS

J. D. Winefordner, Series Editor

Vol.

1.

The Analytical Chemistry of Industrial Poisons, Hazards, and Solvents.

Second Edition.

By the late Morris B. Jacobs

Vol.

2.

Chromatographic Adsorption Analysis.

By Harold H. Strain (

out of print

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Vol.

3.

Photometric Determination of Traces of Metals.

Fourth Edition

Part I: General Aspects. By E. B. Sandell and Hiroshi OnishiPart IIA: Individual Metals, Aluminum to Lithium. By Hiroshi OnishiPart IIB: Individual Metals, Magnesium to Zirconium. By Hiroshi Onishi

Vol.

4.

Organic Reagents Used in Gravimetric and Volumetric Analysis.

By John F. Flagg (

out of print

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Vol.

5.

Aquametry: A Treatise on Methods for the Determination of Water.

Second Edition (in three parts).

By John Mitchell, Jr. and Donald Milton Smith

Vol.

6.

Analysis of Insecticides and Acaricides.

By Francis A. Gunther and Roger C. Blinn (

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Vol.

7.

Chemical Analysis of Industrial Solvents.

By the late Morris B. Jacobs and Leopold Schetlan

Vol.

8.

Colorimetric Determination of Nonmetals.

Second Edition.

Edited by the late David F. Boltz and James A. Howell

Vol.

9.

Analytical Chemistry of Titanium Metals and Compounds.

By Maurice Codell

Vol.

10.

The Chemical Analysis of Air Pollutants.

By the late Morris B. Jacobs

Vol.

11.

X-Ray Spectrochemical Analysis.

Second Edition.

By L. S. Birks

Vol.

12.

Systematic Analysis of Surface-Active Agents.

Second Edition.

By Milton J. Rosen and Henry A. Goldsmith

Vol.

13.

Alternating Current Polarography and Tensammetry.

By B. Breyer and H. H. Bauer

Vol.

14.

Flame Photometry.

By R. Herrmann and J. Alkemade

Vol.

15.

The Titration of Organic Compounds

(

in two parts

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Vol.

16.

Complexation in Analytical Chemistry: A Guide for the Critical Selection of Analytical Methods Based on Complexation Reactions.

By the late Anders Ringbom

Vol.

17.

Electron Probe Microanalysis.

Second Edition.

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Vol.

18.

Organic Completing Reagents: Structure, Behavior, and Application to Inorganic Analysis.

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Vol.

19.

Thermal Analysis.

Third Edition.

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Vol.

20.

Amperometric Titrations.

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Vol.

21.

Reflectance Spectroscopy.

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The Analytical Toxicology of Industrial Inorganic Poisons.

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The Formation and Properties of Precipitates.

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Kinetics in Analytical Chemistry.

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Atomic Absorption Spectroscopy.

Second Edition.

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(

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27.

Rock and Mineral Analysis.

Second Edition.

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The Analytical Chemistry of Nitrogen and Its Compounds

(

in two parts

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29.

The Analytical Chemistry of Sulfur and Its Compounds

(

in three parts

). By J. H. Karchmer

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30.

Ultramicro Elemental Analysis.

By Günther Tölg

Vol.

31.

Photometric Organic Analysis

(

in two parts

). By Eugene Sawicki

Vol.

32.

Determination of Organic Compounds: Methods and Procedures.

By Frederick T. Weiss

Vol.

33.

Masking and Demasking of Chemical Reactions.

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Vol.

34.

Neutron Activation Analysis.

By D. De Soete, R. Gijbels, and J. Hoste

Vol.

35.

Laser Raman Spectroscopy.

By Marvins C. Tobin

Vol.

36.

Emission Spectrochemical Analysis.

By Morris Slavin

Vol.

37.

Analytical Chemistry of Phosphorus Compounds.

Edited by M. Halmann

Vol.

38.

Luminescence Spectroscopy in Analytical Chemistry.

By J. D. Winefordner, S. G. Schulman, and T. C. O’Haver

Vol.

39.

Activation Analysis with Neutron Generators.

By Sam S. Nargolwalla and Edwin P. Przybylowicz

Vol.

40.

Determination of Gaseous Elements in Metals.

Edited by Lynn L. Lewis, Laben M. Melnick, and Ben D. Holt

Vol.

41.

Analysis of Silicones.

Edited by A. Lee Smith

Vol.

42.

Foundations of Ultracentrifugal Analysis.

By H. Fujita

Vol.

43.

Chemical Infrared Fourier Transform Spectroscopy.

By Peter R. Griffiths

Vol.

44.

Microscale Manipulations in Chemistry.

By T. S. Ma and V. Horak

Vol.

45.

Thermometric Titrations.

By J. Barthel

Vol.

46.

Trace Analysis:

Spectroscopic Methods for Elements. Edited by J. D. Winefordner

Vol.

47.

Contamination Control in Trace Element Analysis.

By Morris Zief and James W. Mitchell

Vol.

48.

Analytical Applications of NMR.

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Vol.

49.

Measurement of Dissolved Oxygen.

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Vol.

50.

Analytical Laser Spectroscopy.

Edited by Nicolo Omenetto

Vol.

51.

Trace Element Analysis of Geological Materials.

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Vol.

52.

Chemical Analysis by Microwave Rotational Spectroscopy.

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Vol.

53.

Information Theory as Applied to Chemical Analysis.

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Vol.

54.

Applied Infrared Spectroscopy: Fundamentals, Techniques, and Analytical Problem-Solving.

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Vol.

55.

Archaeological Chemistry.

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Vol.

56.

Immobilized Enzymes in Analytical and Clinical Chemistry.

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Vol.

57.

Photoacoustics and Photoacoustic Spectroscopy.

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Vol.

58.

Analysis of Pesticide Residues.

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Vol.

59.

Affinity Chromatography.

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Vol.

60.

Quality Control in Analytical Chemistry.

Second Edition.

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Vol.

61.

Direct Characterization of Fineparticles.

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Vol.

62.

Flow Injection Analysis.

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Vol.

63.

Applied Electron Spectroscopy for Chemical Analysis.

Edited by Hassan Windawi and Floyd Ho

Vol.

64.

Analytical Aspects of Environmental Chemistry.

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Vol.

65.

The Interpretation of Analytical Chemical Data by the Use of Cluster Analysis.

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Vol.

66.

Solid Phase Biochemistry: Analytical and Synthetic Aspects.

Edited by William H. Scouten

Vol.

67.

An Introduction to Photoelectron Spectroscopy.

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Vol.

68.

Room Temperature Phosphorimetry for Chemical Analysis.

By Tuan Vo-Dinh

Vol.

69.

Potentiometry and Potentiometric Titrations.

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Vol.

70.

Design and Application of Process Analyzer Systems.

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Vol.

71.

Analysis of Organic and Biological Surfaces.

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Vol.

72.

Small Bore Liquid Chromatography Columns: Their Properties and Uses.

Edited by Raymond P. W. Scott

Vol.

73.

Modern Methods of Particle Size Analysis.

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Vol.

74.

Auger Electron Spectroscopy.

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Vol.

75.

Spot Test Analysis: Clinical, Environmental, Forensic and Geochemical Applications.

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Vol.

76.

Receptor Modeling in Environmental Chemistry.

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Vol.

77.

Molecular Luminescence Spectroscopy: Methods and Applications

(

in three parts

). Edited by Stephen G. Schulman

Vol.

78.

Inorganic Chromatographic Analysis.

By John C. MacDonald

Vol.

79.

Analytical Solution Calorimetry.

Edited by J. K. Grime

Vol.

80.

Selected Methods of Trace Metal Analysis: Biological and Environmental Samples.

By Jon C. VanLoon

Vol.

81.

The Analysis of Extraterrestrial Materials.

By Isidore Adler

Vol.

82.

Chemometrics.

By Muhammad A. Sharaf. Deborah L. Illman, and Bruce R. Kowalski

Vol.

83.

Fourier Transform Infrared Spectrometry.

By Peter R. Griffiths and James A. de Haseth

Vol.

84.

Trace Analysis: Spectroscopic Methods for Molecules.

Edited by Gary Christian and James B. Callis

Vol.

85.

Ultratrace Analysis of Pharmaceuticals and Other Compounds of Interest.

Edited by S. Ahuja

Vol.

86.

Secondary Ion Mass Spectrometry: Basic Concepts, Instrumental Aspects, Applications and Trends.

By A. Benninghoven, F. G. Rüdenauer, and H. W. Werner

Vol.

87.

Analytical Applications of Lasers.

Edited by Edward H. Piepmeier

Vol.

88.

Applied Geochemical Analysis

By C. O. Ingamells and F. F. Pitard

Vol.

89.

Detectors for Liquid Chromatography.

Edited by Edward S. Yeung

Vol.

90.

Inductively Coupled Plasma Emission Spectroscopy: Part I: Methodology, Instrumentation, and Performance; Part II: Applications and Fundamentals.

Edited by J. M. Boumans

Vol.

91.

Applications of New Mass Spectrometry Techniques in Pesticide Chemistry.

Edited by Joseph Rosen

Vol.

92.

X-Ray Absorption: Principles, Applications, Techniques of EXAFS, SEXAFS, and XANES.

Edited by D. C. Konnigsberger

Vol.

93.

Quantitative Structure-Chromatographic Retention Relationships.

By Roman Kaliszan

Vol.

94.

Laser Remote Chemical Analysis.

Edited by Raymond M. Measures

Vol.

95.

Inorganic Mass Spectrometry.

Edited by F. Adams, R. Gijbels, and R. Van Grieken

Vol.

96.

Kinetic Aspects of Analytical Chemistry.

By Horacio A. Mottola

Vol.

97.

Two-Dimensional NMR Spectroscopy.

By Jan Schraml and Jon M. Bellama

Vol.

98.

High Performance Liquid Chromatography.

Edited by Phyllis R. Brown and Richard A. Hartwick

Vol.

99.

X-Ray Fluorescence Spectrometry.

By Ron Jenkins

Vol.

100.

Analytical Aspects of Drug Testing.

Edited by Dale G. Deustch

Vol.

101.

Chemical Analysis of Polycyclic Aromatic Compounds.

Edited by Tuan Vo-Dinh

Vol.

102.

Quadrupole Storage Mass Spectrometry.

By Raymond E. March and Richard J. Hughes

Vol.

103.

Determination of Molecular Weight.

Edited by Anthony R. Cooper

Vol.

104.

Selectivity and Detectability Optimization in HPLC.

By Satinder Ahuja

Vol.

105.

Laser Microanalysis.

By Lieselotte Moenke-Blankenburg

Vol.

106.

Clinical Chemistry.

Edited by E. Howard Taylor

Vol.

107.

Multielement Detection Systems for Spectrochemical Analysis.

By Kenneth W. Busch and Marianna A. Busch

Vol.

108.

Planar Chromatography in the Life Sciences.

Edited by Joseph C. Touchstone

Vol.

109.

Fluorometric Analysis in Biomedical Chemistry: Trends and Techniques Including HPLC Applications.

By Norio Ichinose, George Schwedt, Frank Michael Schnepel, and Kyoko Adochi

Vol.

110.

An Introduction to Laboratory Automation.

By Victor Cerdá and Guillermo Ramis

Vol.

111.

Gas Chromatography: Biochemical, Biomedical, and Clinical Applications.

Edited by Ray E. Clement

Vol.

112.

The Analytical Chemistry of Silicones.

Edited by A. Lee Smith

Vol.

113.

Modern Methods of Polymer Characterization.

Edited by Howard G. Barth and Jimmy W. Mays

Vol.

114.

Analytical Raman Spectroscopy.

Edited by Jeanette Graselli and Bernard J. Bulkin

Vol.

115.

Trace and Ultratrace Analysis by HPLC.

By Satinder Ahuja

Vol.

116.

Radiochemistry and Nuclear Methods of Analysis.

By William D. Ehmann and Diane E. Vance

Vol.

117.

Applications of Fluorescence in Immunoassays.

By Ilkka Hemmila

Vol.

118.

Principles and Practice of Spectroscopic Calibration.

By Howard Mark

Vol.

119.

Activation Spectrometry in Chemical Analysis.

By S. J. Parry

Vol.

120.

Remote Sensing by Fourier Transform Spectrometry.

By Reinhard Beer

Vol.

121.

Detectors for Capillary Chromatography.

Edited by Herbert H. Hill and Dennis McMinn

Vol.

122.

Photochemical Vapor Deposition.

By J. G. Eden

Vol.

123.

Statistical Methods in Analytical Chemistry.

By Peter C. Meier and Richard Zund

Vol.

124.

Laser Ionization Mass Analysis.

Edited by Akos Vertes, Renaat Gijbels, and Fred Adams

Vol.

125.

Physics and Chemistry of Solid State Sensor Devices.

By Andreas Mandelis and Constantinos Christofides

Vol.

126.

Electroanalytical Stripping Methods.

By Khjena Z. Brainina and E. Neyman

Vol.

127.

Air Monitoring by Spectroscopic Techniques.

Edited by Markus W. Sigrist

Vol.

128.

Information Theory in Analytical Chemistry.

By Karel Eckschlager and Klaus Danzer

Vol.

129.

Flame Chemiluminescence Analysis by Molecular Emission Cavity Detection.

Edited by David Stiles, Anthony Calokerinos, and Alan Townshend

Vol.

130.

Hydride Generation Atomic Absorption Spectrometry.

Edited by Jiri Dedina and Dimiter L. Tsalev

Vol.

131.

Selective Detectors: Environmental, Industrial, and Biomedical Applications.

Edited by Robert E. Sievers

Vol.

132.

High-Speed Countercurrent Chromatography.

Edited by Yoichiro Ito and Walter D. Conway

Vol.

133.

Particle-Induced X-Ray Emission Spectrometry.

By Sven A. E. Johansson, John L. Campbell, and Klas G. Malmqvist

Vol.

134.

Photothermal Spectroscopy Methods for Chemical Analysis.

By Stephen E. Bialkowski

Vol.

135.

Element Speciation in Bioinorganic Chemistry.

Edited by Sergio Caroli

Vol.

136.

Laser-Enhanced Ionization Spectrometry.

Edited by John C. Travis and Gregory C. Turk

Vol.

137.

Fluorescence Imaging Spectroscopy and Microscopy.

Edited by Xue Feng Wang and Brian Herman

Vol.

138.

Introduction to X-Ray Powder Diffractometry.

By Ron Jenkins and Robert L. Snyder

Vol.

139.

Modern Techniques in Electroanalysis.

Edited by Petr Vanýsek

Vol.

140.

Total-Reflection X-Ray Fluorescence Analysis.

By Reinhold Klockenkamper

Vol.

141.

Spot Test Analysis: Clinical, Environmental, Forensic, and Geochemical Applications

,

Second Edition.

By Ervin Jungreis

Vol.

142.

The Impact of Stereochemistry on Drug Development and Use.

Edited by Hassan Y. Aboul-Enein and Irving W. Wainer

Vol.

143.

Macrocyclic Compounds in Analytical Chemistry.

Edited by Yury A. Zolotov

Vol.

144.

Surface-Launched Acoustic Wave Sensors: Chemical Sensing and Thin-Film Characterization.

By Michael Thompson and David Stone

Vol.

145.

Modern Isotope Ratio Mass Spectrometry.

Edited by T. J. Platzner

Vol.

146.

High Performance Capillary Electrophoresis: Theory, Techniques, and Applications.

Edited by Morteza G. Khaledi

Vol.

147.

Solid Phase Extraction: Principles and Practice.

By E. M. Thurman

Vol.

148.

Commercial Biosensors: Applications to Clinical, Bioprocess, and Environmental Samples.

Edited by Graham Ramsay

Vol.

149.

A Practical Guide to Graphite Furnace Atomic Absorption Spectrometry.

By David J. Butcher and Joseph Sneddon

Vol.

150.

Principles of Chemical and Biological Sensors.

Edited by Dermot Diamond

CHAPTER 1

PRODUCTION AND PROPERTIES X-RAYS

1.1. INTRODUCTION

X-rays are a short wavelength form of electromagnetic radiation discovered by Wilhelm Röntgen in 1895 [1]. X-ray based techniques provided important tools for theoretical physicists in the first half of this century and, since the early 1950s, they have found an increasing use in the field of materials characterization. Today, methods based on absoptiometry play a vital role in industrial and medical radiography. The simple X-ray field units employed in World War I were responsible for saving literally tens of thousands of lives, [2] and today the technology has advanced to a high degree of sophistication. Modern X-ray tomographic methods give an almost complete three-dimensional cross section of the human body, offering an incredibly powerful tool for the medical field. In addition, the analytical techniques based on X-ray diffraction and X-ray spectrometry, both of which were first conceived almost 70 years ago, have become indispensable in the analysis and study of inorganic and organic solids. Today, data obtained from X-ray spectrometers are being used to control steel mills, ore flotation processes, cement kilns, and a whole host of other vital industrial processes (see e.g., [3]). X-ray diffractometers are used for the study of ore and mineral deposits, in the production of drugs and pharmaceuticals, in the study of thin films, stressed and oriented materials, phase transformations, plus myriad other applications in pure and applied research.

X-ray photons are produced following the ejection of an inner orbital electron from an irradiated atom, and subsequent transition of atomic orbital electrons from states of high to low energy. When a monochromatic beam of X-ray photons falls onto a given specimen, three basic phenomena may result, namely, scatter, absorption or fluorescence. The coherently scattered photons may undergo subsequent interference leading in turn to the generation of diffraction maxima. The angles at which the diffraction maxima occur can be related to the spacings between planes of atoms in the crystal lattice and hence, X-ray generated diffraction patterns can be used to study the structure of solid materials. Following the discovery of the diffraction of X-rays by Max Von Laue in 1913 [4], the use of this method for materials analysis has become very important both in industry and research. Today, it is one of the most useful techniques available for the study of structure dependant properties of materials.

X-ray powder diffractometry involves characterization of materials by use of data dependant on the atomic arrangement in the crystal lattice (see e.g., [5]). The technique uses single or multiphase (i.e., multicomponent) specimens comprising a random orientation of small crystallites, each of the order of 1 to 50 μm in diameter. Each crystallite in turn is made up of a regular, ordered array of atoms. An ordered arrangement of atoms (the crystal lattice) contains planes of high atomic density that in turn means planes of high electron density. A monochromatic beam of X-ray photons will be scattered by these atomic electrons and, if the scattered photons interfere with each other, diffraction maxima may occur. In general, one diffracted line will occur for each unique set of planes in the lattice. A diffraction pattern is typically in the form of a graph of diffraction angle (or interplanar spacing) versus diffracted line intensity. The pattern is thus made up of a series of superimposed diffractograms, one for each unique phase in the specimen. Each of these unique patterns can act as an empirical “fingerprint” for the identification of the various phases, using pattern recognition techniques based on a file of standard single-phase patterns. Quantitative phase analysis is also possible, albeit with some difficulty, because of various experimental and other problems, not the least of which is the large number of diffraction lines occurring from multiphase materials.

A beam of X-rays passing through matter will be attenuated by two processes, scatter and photoelectric absorption. In the majority of cases the greater of these two effects is absorption and the magnitude of the absorption process, that is, the fraction of incident X-ray photons lost in passing through the absorber increases significantly with the average atomic number of the absorbing medium. To a first approximation, the mass attenuation coefficient varies as the third power of the atomic number of the absorber. Thus, when a polychromatic beam of X-rays is passed through a heterogeneous material, areas of higher average atomic number will attenuate the beam to a greater extent than areas of lower atomic number. Thus the beam of radiation emerging from the absorber has an intensity distribution across the irradiation area of the specimen, which is related to the average atomic number distribution across the same area. It is upon this principle that all methods of X-ray radiography are based. Study of materials by use of the X-ray absorption process is the oldest of all of the X-ray methods in use. Röntgen himself included a radiograph of his wife’s hand in his first published X-ray paper. Today, there are many different forms of X-ray absorptiometry in use, including industrial radiography, diagnostic medical and dental radiography, and security screening.

Secondary radiation produced from the specimen is characteristic of the elements making up the specimen. The technique used to isolate and measure individual characteristic wavelengths is called X-ray spectrometry. X-ray spectrometry also has its roots in the early part of this century, stemming from Moseley’s work in 1913 [6]. This technique uses either the diffracting power of a single crystal to isolate narrow wavelength bands, or a proportional detector to isolate narrow energy bands, from the polychromatic beam characteristic radiation excited in the sample. The first of these methods is called Wavelength Dispersive Spectrometry and the second, Energy Dispersive Spectrometry. Because the relationship between emission wavelength and atomic number is known, isolation of individual characteristic lines allows the unique identification of an element to be made and elemental concentrations can be estimated from characteristic line intensities. Thus this technique is a means of materials characterization in terms of chemical composition.

Although the major thrust of this monograph is to review X-ray spectroscopic techniques, these are by no means the only X-ray-based methods that are used for materials analysis and characterization. In addition to the many industrial and medical applications of diagnostic X-ray absorption methods already mentioned, X-rays are also used in areas such as structure determination based on single crystal techniques, space exploration and research, lithography for the production of microelectronic circuits, and so on. One of the major limitations leading to the further development of new X-ray methods is the inability to focus X-rays, as can be done with visible light rays. Although it is possible to partially reflect X- rays at low glancing angles, or diffract an X-ray beam with a single crystal, these methods cause significant intensity loss, and fall far short of providing the high intensity, monochromatic beam that would be ideal for such uses as an X-ray microscope. Use of synchrotron radiation offers the potential of an intense, highly focused, coherent X-ray beam, but has practical limitations due to size and cost. The X-ray laser could, in principle, provide an attractive alternative, and since the discovery of the laser in 1960, the possibilities of such an X-ray laser have been discussed. Although major research efforts have been, and are still being, made to produce laser action in the far ultraviolet and soft X-ray regions, production of conditions to stimulate laser action in the X-ray region with a net positive gain is difficult. This is due mainly to the rapid decay rates and high absorption cross sections that are experienced in practice.

1.2. CONTINUOUS RADIATION

Figure 1.1 Intensity output from a molybdenum target X-ray at 10, 20, and 30 kV.

1.3. CHARACTERISTIC RADIATION

If a high energy particle, such as an electron, strikes a bound atomic electron, and the energy E of the particle is greater than the binding energy φ of the atomic electron, it is possible that the atomic electron will be ejected from its atomic position, departing from the atom with a kinetic energy (E-φ), equivalent to the difference between that of the initial particle and the binding energy of the atomic electron. The ejected electron is called a photoelectron and the interaction is referred to as the photoelectric effect. While the fate of the ejected photoelectron has little consequence as far as the production and use of characteristic X-radiation from an atom is concerned, it should be mentioned that study of the energy distribution of the emitted photoelectrons gives valuable information about bonding and atomic structure [7]. Study of such information forms the basis of the technique of photoelectron spectroscopy (see e.g., [8]). As long as the vacancy in the shell exists, the atom is in an unstable state and there are two processes by which the atom can revert back to its original state. The first of these involves a rearrangement that does not result in the emission of X-ray photons, but in the emission of other photoelectrons from the atom. The effect is known as the Auger effect, and the emitted photoelectrons are called Auger electrons. The second process by which the excited atom can regain stability is by transference of an electron from one of the outer orbitals to fill the vacancy. The energy difference between the initial and final states of the transferred electron may be given off in the form of an X-ray photon. Since all emitted X-ray photons have energies proportional to the differences in the energy states of atomic electrons, the lines from a given element will be characteristic of that element. The relationship between the wavelength λ of a characteristic X-ray photon and the atomic number Z of the excited element was first established by Moseley (see Chapter 4). Moseley’s law is written

(1.1)

in which K is a constant that takes on different values for each spectral series. σ is the shielding constant that has a value of just less than unity. The wavelength of the X-ray photon is inversely related to the energy E of the photon according to the relationship

(1.2)

There are several different combinations of quantum numbers held by the electron in the initial and final states, hence several different X-ray wavelengths will be emitted from a given atom. For those vacancies giving rise to characteristic X-ray photons, a series of very simple selection rules can be used to define which electrons can be transferred. For a detailed explanation of these rules, refer to Section 4.4. Briefly, the principal quantum number n must change by 1, the angular quantum number must change by 1, and the vector sum of ( + s) must be a number changing by 1 or 0. In effect this means that for the K series only p → s transitions are allowed, yielding two lines for each principle level change. Vacancies in the L level follow similar rules and give rise to L series lines. There are more of the L lines since p → s, s → p, and d → p transitions are all allowed within the selection rules. In general, electron transitions to the K shell give between two and six K lines, and transitions to the L shell give about twelve strong to moderately strong L lines.

Because there are two competing effects by which an atom may return to its initial state, and because only one of these processes will give rise to the production of a characteristic X-ray photon, the intensity of an emitted characteristic X-ray beam will be dependant upon the relative effectiveness of the two processes within a given atom. As an example, the number of quanta of K series radiation emitted per ionized atom, is a fixed ratio for a given atomic number. This ratio is called the fluorescent yield.

Figure 1.2 Fluorescence yield as a function of atomic number.

1.4. ABSORPTION OF X-RAYS

All matter is made up of molecules, each consisting of a group of atoms. Each atom is in turn made up of a nucleus surrounded by electrons in discrete energy levels. The number of electrons is equal to the atomic number of the atom, when the atom is in the ground state. When a beam of X-ray photons is incident upon matter, the photons may interact with the individual atomic electrons.

The processes involved in the excitation of a characteristic wavelength λf by an incident X-ray beam λ0 are illustrated in Figure 1.3. Here a beam of X-ray photons of intensity I0(λ0) falls onto a specimen at an incident angle ψ1. A portion of the beam will pass through the absorber, the fraction being given by the expression

Figure 1.3 Interaction of the primary X-ray beam with the sample.

(1.3)

where μ is the mass attenuation coefficient of absorber for the wavelength and ρ the density of the specimen, x is the distance traveled through the specimen and this is related to the thickness T of the specimen by the sine of the incident angle ψ1. Note that as far as the primary wavelengths are concerned, three processes occur. The first of these is the attenuation of the transmitted beam as described above. Secondly, the primary beam may be scattered over an angle ψ and emerge as coherently and incoherently scattered wavelengths. Thirdly, fluorescence radiation may also arise from the sample. The depth d of the specimen contributing to the fluorescence intensity is related to the attenuation coefficient of the sample for the fluorescence wavelength, and the angle of emergence ψ2 at the fluorescence beam is observed. It can be seen from Equation 1.3 that a number (I0 - I) of photons has been lost in the absorption process. Although a significant fraction of this loss may be due to scatter, by far the greater loss is due to the photoelectric effect. It is important to differentiate between mass absorption coefficient and mass attenuation coefficient. The mass absorption coefficient is dependant only on photoelectric interaction between the incident beam and atomic photons produced within the specimen. The mass attenuation coefficient also includes scattering of the primary beam. Thus, for most quantitative X-ray spectrometry, the mass attenuation coefficient should be employed. Photoelectric absorption occurs at each of the energy levels of the atom, thus the total photoelectric absorption is determined by the sum of each individual absorption within a specific shell. Where the absorber is made up of a number of different elements, as is usually the case, the total attenuation is made up of the sum of the products of the individual elemental mass absorption coefficients and the weight fractions of the respective elements. This product is referred to as the total matrix absorption. The value of the mass attenuation referred to in Equation 1.3 is a function of both the photoelectric absorption and the scatter. However, the photoelectric absorption influence is usually large compared to the photoelectric absorption.

The photoelectric absorption is made up of absorption in the various atomic levels and it is an atomic number dependant function. A plot of the mass absorption coefficient as a function of wavelength contains a number of discontinuities called absorption edges, at wavelengths corresponding to the binding energies of the electrons in the various subshells. As an example, Figure 1.4 shows a plot of the mass absorption coefficient as a function of wavelength for the element barium. It can be seen that as the wavelength of the incident X-ray photons becomes longer, the absorption increases. A number of discontinuities are also seen in the absorption curve, one K discontinuity, three L discontinuities and five M discontinuities. Since it can be assumed that the mass attenuation coefficient is proportional to the total photoelectric absorption, as indicated at the bottom of the figure, an equation can be written that shows that the total photoelectric absorption is made up of absorption in the K level, plus absorption in the three L levels, and so on. The figure also shows the magnitudes of the various contributions of the levels to the total value of the absorption coefficient of 262/g for barium at a wavelength of 0.3 Å. It can be seen that the contributions from K, L, and M levels, respectively, are 18, 7.5, and 0.45, with 0.05 coming from other outer levels. If a slightly longer wavelength were chosen, say perhaps 0.6 Å, the wavelength would fall on the long wavelength side of the K absorption edge. This being the case, these photons are insufficiently energetic to eject K electrons from the barium, and since there can be no photoelectric absorption in the level, the term for the K level drops out of the equation. Since this K term is large in comparison to the others, there is a sudden drop in the absorption curve corresponding exactly to the wavelength at which photoelectric absorption in the K level can no longer occur.

Figure 1.4 Mass absorption coefficient for barium, showing individual contributions from K, L and M subshells.