- •Preface
- •Imaging Microscopic Features
- •Measuring the Crystal Structure
- •References
- •Contents
- •1.4 Simulating the Effects of Elastic Scattering: Monte Carlo Calculations
- •What Are the Main Features of the Beam Electron Interaction Volume?
- •How Does the Interaction Volume Change with Composition?
- •How Does the Interaction Volume Change with Incident Beam Energy?
- •How Does the Interaction Volume Change with Specimen Tilt?
- •1.5 A Range Equation To Estimate the Size of the Interaction Volume
- •References
- •2: Backscattered Electrons
- •2.1 Origin
- •2.2.1 BSE Response to Specimen Composition (η vs. Atomic Number, Z)
- •SEM Image Contrast with BSE: “Atomic Number Contrast”
- •SEM Image Contrast: “BSE Topographic Contrast—Number Effects”
- •2.2.3 Angular Distribution of Backscattering
- •Beam Incident at an Acute Angle to the Specimen Surface (Specimen Tilt > 0°)
- •SEM Image Contrast: “BSE Topographic Contrast—Trajectory Effects”
- •2.2.4 Spatial Distribution of Backscattering
- •Depth Distribution of Backscattering
- •Radial Distribution of Backscattered Electrons
- •2.3 Summary
- •References
- •3: Secondary Electrons
- •3.1 Origin
- •3.2 Energy Distribution
- •3.3 Escape Depth of Secondary Electrons
- •3.8 Spatial Characteristics of Secondary Electrons
- •References
- •4: X-Rays
- •4.1 Overview
- •4.2 Characteristic X-Rays
- •4.2.1 Origin
- •4.2.2 Fluorescence Yield
- •4.2.3 X-Ray Families
- •4.2.4 X-Ray Nomenclature
- •4.2.6 Characteristic X-Ray Intensity
- •Isolated Atoms
- •X-Ray Production in Thin Foils
- •X-Ray Intensity Emitted from Thick, Solid Specimens
- •4.3 X-Ray Continuum (bremsstrahlung)
- •4.3.1 X-Ray Continuum Intensity
- •4.3.3 Range of X-ray Production
- •4.4 X-Ray Absorption
- •4.5 X-Ray Fluorescence
- •References
- •5.1 Electron Beam Parameters
- •5.2 Electron Optical Parameters
- •5.2.1 Beam Energy
- •Landing Energy
- •5.2.2 Beam Diameter
- •5.2.3 Beam Current
- •5.2.4 Beam Current Density
- •5.2.5 Beam Convergence Angle, α
- •5.2.6 Beam Solid Angle
- •5.2.7 Electron Optical Brightness, β
- •Brightness Equation
- •5.2.8 Focus
- •Astigmatism
- •5.3 SEM Imaging Modes
- •5.3.1 High Depth-of-Field Mode
- •5.3.2 High-Current Mode
- •5.3.3 Resolution Mode
- •5.3.4 Low-Voltage Mode
- •5.4 Electron Detectors
- •5.4.1 Important Properties of BSE and SE for Detector Design and Operation
- •Abundance
- •Angular Distribution
- •Kinetic Energy Response
- •5.4.2 Detector Characteristics
- •Angular Measures for Electron Detectors
- •Elevation (Take-Off) Angle, ψ, and Azimuthal Angle, ζ
- •Solid Angle, Ω
- •Energy Response
- •Bandwidth
- •5.4.3 Common Types of Electron Detectors
- •Backscattered Electrons
- •Passive Detectors
- •Scintillation Detectors
- •Semiconductor BSE Detectors
- •5.4.4 Secondary Electron Detectors
- •Everhart–Thornley Detector
- •Through-the-Lens (TTL) Electron Detectors
- •TTL SE Detector
- •TTL BSE Detector
- •Measuring the DQE: BSE Semiconductor Detector
- •References
- •6: Image Formation
- •6.1 Image Construction by Scanning Action
- •6.2 Magnification
- •6.3 Making Dimensional Measurements With the SEM: How Big Is That Feature?
- •Using a Calibrated Structure in ImageJ-Fiji
- •6.4 Image Defects
- •6.4.1 Projection Distortion (Foreshortening)
- •6.4.2 Image Defocusing (Blurring)
- •6.5 Making Measurements on Surfaces With Arbitrary Topography: Stereomicroscopy
- •6.5.1 Qualitative Stereomicroscopy
- •Fixed beam, Specimen Position Altered
- •Fixed Specimen, Beam Incidence Angle Changed
- •6.5.2 Quantitative Stereomicroscopy
- •Measuring a Simple Vertical Displacement
- •References
- •7: SEM Image Interpretation
- •7.1 Information in SEM Images
- •7.2.2 Calculating Atomic Number Contrast
- •Establishing a Robust Light-Optical Analogy
- •Getting It Wrong: Breaking the Light-Optical Analogy of the Everhart–Thornley (Positive Bias) Detector
- •Deconstructing the SEM/E–T Image of Topography
- •SUM Mode (A + B)
- •DIFFERENCE Mode (A−B)
- •References
- •References
- •9: Image Defects
- •9.1 Charging
- •9.1.1 What Is Specimen Charging?
- •9.1.3 Techniques to Control Charging Artifacts (High Vacuum Instruments)
- •Observing Uncoated Specimens
- •Coating an Insulating Specimen for Charge Dissipation
- •Choosing the Coating for Imaging Morphology
- •9.2 Radiation Damage
- •9.3 Contamination
- •References
- •10: High Resolution Imaging
- •10.2 Instrumentation Considerations
- •10.4.1 SE Range Effects Produce Bright Edges (Isolated Edges)
- •10.4.4 Too Much of a Good Thing: The Bright Edge Effect Hinders Locating the True Position of an Edge for Critical Dimension Metrology
- •10.5.1 Beam Energy Strategies
- •Low Beam Energy Strategy
- •High Beam Energy Strategy
- •Making More SE1: Apply a Thin High-δ Metal Coating
- •Making Fewer BSEs, SE2, and SE3 by Eliminating Bulk Scattering From the Substrate
- •10.6 Factors That Hinder Achieving High Resolution
- •10.6.2 Pathological Specimen Behavior
- •Contamination
- •Instabilities
- •References
- •11: Low Beam Energy SEM
- •11.3 Selecting the Beam Energy to Control the Spatial Sampling of Imaging Signals
- •11.3.1 Low Beam Energy for High Lateral Resolution SEM
- •11.3.2 Low Beam Energy for High Depth Resolution SEM
- •11.3.3 Extremely Low Beam Energy Imaging
- •References
- •12.1.1 Stable Electron Source Operation
- •12.1.2 Maintaining Beam Integrity
- •12.1.4 Minimizing Contamination
- •12.3.1 Control of Specimen Charging
- •12.5 VPSEM Image Resolution
- •References
- •13: ImageJ and Fiji
- •13.1 The ImageJ Universe
- •13.2 Fiji
- •13.3 Plugins
- •13.4 Where to Learn More
- •References
- •14: SEM Imaging Checklist
- •14.1.1 Conducting or Semiconducting Specimens
- •14.1.2 Insulating Specimens
- •14.2 Electron Signals Available
- •14.2.1 Beam Electron Range
- •14.2.2 Backscattered Electrons
- •14.2.3 Secondary Electrons
- •14.3 Selecting the Electron Detector
- •14.3.2 Backscattered Electron Detectors
- •14.3.3 “Through-the-Lens” Detectors
- •14.4 Selecting the Beam Energy for SEM Imaging
- •14.4.4 High Resolution SEM Imaging
- •Strategy 1
- •Strategy 2
- •14.5 Selecting the Beam Current
- •14.5.1 High Resolution Imaging
- •14.5.2 Low Contrast Features Require High Beam Current and/or Long Frame Time to Establish Visibility
- •14.6 Image Presentation
- •14.6.1 “Live” Display Adjustments
- •14.6.2 Post-Collection Processing
- •14.7 Image Interpretation
- •14.7.1 Observer’s Point of View
- •14.7.3 Contrast Encoding
- •14.8.1 VPSEM Advantages
- •14.8.2 VPSEM Disadvantages
- •15: SEM Case Studies
- •15.1 Case Study: How High Is That Feature Relative to Another?
- •15.2 Revealing Shallow Surface Relief
- •16.1.2 Minor Artifacts: The Si-Escape Peak
- •16.1.3 Minor Artifacts: Coincidence Peaks
- •16.1.4 Minor Artifacts: Si Absorption Edge and Si Internal Fluorescence Peak
- •16.2 “Best Practices” for Electron-Excited EDS Operation
- •16.2.1 Operation of the EDS System
- •Choosing the EDS Time Constant (Resolution and Throughput)
- •Choosing the Solid Angle of the EDS
- •Selecting a Beam Current for an Acceptable Level of System Dead-Time
- •16.3.1 Detector Geometry
- •16.3.2 Process Time
- •16.3.3 Optimal Working Distance
- •16.3.4 Detector Orientation
- •16.3.5 Count Rate Linearity
- •16.3.6 Energy Calibration Linearity
- •16.3.7 Other Items
- •16.3.8 Setting Up a Quality Control Program
- •Using the QC Tools Within DTSA-II
- •Creating a QC Project
- •Linearity of Output Count Rate with Live-Time Dose
- •Resolution and Peak Position Stability with Count Rate
- •Solid Angle for Low X-ray Flux
- •Maximizing Throughput at Moderate Resolution
- •References
- •17: DTSA-II EDS Software
- •17.1 Getting Started With NIST DTSA-II
- •17.1.1 Motivation
- •17.1.2 Platform
- •17.1.3 Overview
- •17.1.4 Design
- •Simulation
- •Quantification
- •Experiment Design
- •Modeled Detectors (. Fig. 17.1)
- •Window Type (. Fig. 17.2)
- •The Optimal Working Distance (. Figs. 17.3 and 17.4)
- •Elevation Angle
- •Sample-to-Detector Distance
- •Detector Area
- •Crystal Thickness
- •Number of Channels, Energy Scale, and Zero Offset
- •Resolution at Mn Kα (Approximate)
- •Azimuthal Angle
- •Gold Layer, Aluminum Layer, Nickel Layer
- •Dead Layer
- •Zero Strobe Discriminator (. Figs. 17.7 and 17.8)
- •Material Editor Dialog (. Figs. 17.9, 17.10, 17.11, 17.12, 17.13, and 17.14)
- •17.2.1 Introduction
- •17.2.2 Monte Carlo Simulation
- •17.2.4 Optional Tables
- •References
- •18: Qualitative Elemental Analysis by Energy Dispersive X-Ray Spectrometry
- •18.1 Quality Assurance Issues for Qualitative Analysis: EDS Calibration
- •18.2 Principles of Qualitative EDS Analysis
- •Exciting Characteristic X-Rays
- •Fluorescence Yield
- •X-ray Absorption
- •Si Escape Peak
- •Coincidence Peaks
- •18.3 Performing Manual Qualitative Analysis
- •Beam Energy
- •Choosing the EDS Resolution (Detector Time Constant)
- •Obtaining Adequate Counts
- •18.4.1 Employ the Available Software Tools
- •18.4.3 Lower Photon Energy Region
- •18.4.5 Checking Your Work
- •18.5 A Worked Example of Manual Peak Identification
- •References
- •19.1 What Is a k-ratio?
- •19.3 Sets of k-ratios
- •19.5 The Analytical Total
- •19.6 Normalization
- •19.7.1 Oxygen by Assumed Stoichiometry
- •19.7.3 Element by Difference
- •19.8 Ways of Reporting Composition
- •19.8.1 Mass Fraction
- •19.8.2 Atomic Fraction
- •19.8.3 Stoichiometry
- •19.8.4 Oxide Fractions
- •Example Calculations
- •19.9 The Accuracy of Quantitative Electron-Excited X-ray Microanalysis
- •19.9.1 Standards-Based k-ratio Protocol
- •19.9.2 “Standardless Analysis”
- •19.10 Appendix
- •19.10.1 The Need for Matrix Corrections To Achieve Quantitative Analysis
- •19.10.2 The Physical Origin of Matrix Effects
- •19.10.3 ZAF Factors in Microanalysis
- •X-ray Generation With Depth, φ(ρz)
- •X-ray Absorption Effect, A
- •X-ray Fluorescence, F
- •References
- •20.2 Instrumentation Requirements
- •20.2.1 Choosing the EDS Parameters
- •EDS Spectrum Channel Energy Width and Spectrum Energy Span
- •EDS Time Constant (Resolution and Throughput)
- •EDS Calibration
- •EDS Solid Angle
- •20.2.2 Choosing the Beam Energy, E0
- •20.2.3 Measuring the Beam Current
- •20.2.4 Choosing the Beam Current
- •Optimizing Analysis Strategy
- •20.3.4 Ba-Ti Interference in BaTiSi3O9
- •20.4 The Need for an Iterative Qualitative and Quantitative Analysis Strategy
- •20.4.2 Analysis of a Stainless Steel
- •20.5 Is the Specimen Homogeneous?
- •20.6 Beam-Sensitive Specimens
- •20.6.1 Alkali Element Migration
- •20.6.2 Materials Subject to Mass Loss During Electron Bombardment—the Marshall-Hall Method
- •Thin Section Analysis
- •Bulk Biological and Organic Specimens
- •References
- •21: Trace Analysis by SEM/EDS
- •21.1 Limits of Detection for SEM/EDS Microanalysis
- •21.2.1 Estimating CDL from a Trace or Minor Constituent from Measuring a Known Standard
- •21.2.2 Estimating CDL After Determination of a Minor or Trace Constituent with Severe Peak Interference from a Major Constituent
- •21.3 Measurements of Trace Constituents by Electron-Excited Energy Dispersive X-ray Spectrometry
- •The Inevitable Physics of Remote Excitation Within the Specimen: Secondary Fluorescence Beyond the Electron Interaction Volume
- •Simulation of Long-Range Secondary X-ray Fluorescence
- •NIST DTSA II Simulation: Vertical Interface Between Two Regions of Different Composition in a Flat Bulk Target
- •NIST DTSA II Simulation: Cubic Particle Embedded in a Bulk Matrix
- •21.5 Summary
- •References
- •22.1.2 Low Beam Energy Analysis Range
- •22.2 Advantage of Low Beam Energy X-Ray Microanalysis
- •22.2.1 Improved Spatial Resolution
- •22.3 Challenges and Limitations of Low Beam Energy X-Ray Microanalysis
- •22.3.1 Reduced Access to Elements
- •22.3.3 At Low Beam Energy, Almost Everything Is Found To Be Layered
- •Analysis of Surface Contamination
- •References
- •23: Analysis of Specimens with Special Geometry: Irregular Bulk Objects and Particles
- •23.2.1 No Chemical Etching
- •23.3 Consequences of Attempting Analysis of Bulk Materials With Rough Surfaces
- •23.4.1 The Raw Analytical Total
- •23.4.2 The Shape of the EDS Spectrum
- •23.5 Best Practices for Analysis of Rough Bulk Samples
- •23.6 Particle Analysis
- •Particle Sample Preparation: Bulk Substrate
- •The Importance of Beam Placement
- •Overscanning
- •“Particle Mass Effect”
- •“Particle Absorption Effect”
- •The Analytical Total Reveals the Impact of Particle Effects
- •Does Overscanning Help?
- •23.6.6 Peak-to-Background (P/B) Method
- •Specimen Geometry Severely Affects the k-ratio, but Not the P/B
- •Using the P/B Correspondence
- •23.7 Summary
- •References
- •24: Compositional Mapping
- •24.2 X-Ray Spectrum Imaging
- •24.2.1 Utilizing XSI Datacubes
- •24.2.2 Derived Spectra
- •SUM Spectrum
- •MAXIMUM PIXEL Spectrum
- •24.3 Quantitative Compositional Mapping
- •24.4 Strategy for XSI Elemental Mapping Data Collection
- •24.4.1 Choosing the EDS Dead-Time
- •24.4.2 Choosing the Pixel Density
- •24.4.3 Choosing the Pixel Dwell Time
- •“Flash Mapping”
- •High Count Mapping
- •References
- •25.1 Gas Scattering Effects in the VPSEM
- •25.1.1 Why Doesn’t the EDS Collimator Exclude the Remote Skirt X-Rays?
- •25.2 What Can Be Done To Minimize gas Scattering in VPSEM?
- •25.2.2 Favorable Sample Characteristics
- •Particle Analysis
- •25.2.3 Unfavorable Sample Characteristics
- •References
- •26.1 Instrumentation
- •26.1.2 EDS Detector
- •26.1.3 Probe Current Measurement Device
- •Direct Measurement: Using a Faraday Cup and Picoammeter
- •A Faraday Cup
- •Electrically Isolated Stage
- •Indirect Measurement: Using a Calibration Spectrum
- •26.1.4 Conductive Coating
- •26.2 Sample Preparation
- •26.2.1 Standard Materials
- •26.2.2 Peak Reference Materials
- •26.3 Initial Set-Up
- •26.3.1 Calibrating the EDS Detector
- •Selecting a Pulse Process Time Constant
- •Energy Calibration
- •Quality Control
- •Sample Orientation
- •Detector Position
- •Probe Current
- •26.4 Collecting Data
- •26.4.1 Exploratory Spectrum
- •26.4.2 Experiment Optimization
- •26.4.3 Selecting Standards
- •26.4.4 Reference Spectra
- •26.4.5 Collecting Standards
- •26.4.6 Collecting Peak-Fitting References
- •26.5 Data Analysis
- •26.5.2 Quantification
- •26.6 Quality Check
- •Reference
- •27.2 Case Study: Aluminum Wire Failures in Residential Wiring
- •References
- •28: Cathodoluminescence
- •28.1 Origin
- •28.2 Measuring Cathodoluminescence
- •28.3 Applications of CL
- •28.3.1 Geology
- •Carbonado Diamond
- •Ancient Impact Zircons
- •28.3.2 Materials Science
- •Semiconductors
- •Lead-Acid Battery Plate Reactions
- •28.3.3 Organic Compounds
- •References
- •29.1.1 Single Crystals
- •29.1.2 Polycrystalline Materials
- •29.1.3 Conditions for Detecting Electron Channeling Contrast
- •Specimen Preparation
- •Instrument Conditions
- •29.2.1 Origin of EBSD Patterns
- •29.2.2 Cameras for EBSD Pattern Detection
- •29.2.3 EBSD Spatial Resolution
- •29.2.5 Steps in Typical EBSD Measurements
- •Sample Preparation for EBSD
- •Align Sample in the SEM
- •Check for EBSD Patterns
- •Adjust SEM and Select EBSD Map Parameters
- •Run the Automated Map
- •29.2.6 Display of the Acquired Data
- •29.2.7 Other Map Components
- •29.2.10 Application Example
- •Application of EBSD To Understand Meteorite Formation
- •29.2.11 Summary
- •Specimen Considerations
- •EBSD Detector
- •Selection of Candidate Crystallographic Phases
- •Microscope Operating Conditions and Pattern Optimization
- •Selection of EBSD Acquisition Parameters
- •Collect the Orientation Map
- •References
- •30.1 Introduction
- •30.2 Ion–Solid Interactions
- •30.3 Focused Ion Beam Systems
- •30.5 Preparation of Samples for SEM
- •30.5.1 Cross-Section Preparation
- •30.5.2 FIB Sample Preparation for 3D Techniques and Imaging
- •30.6 Summary
- •References
- •31: Ion Beam Microscopy
- •31.1 What Is So Useful About Ions?
- •31.2 Generating Ion Beams
- •31.3 Signal Generation in the HIM
- •31.5 Patterning with Ion Beams
- •31.7 Chemical Microanalysis with Ion Beams
- •References
- •Appendix
- •A Database of Electron–Solid Interactions
- •A Database of Electron–Solid Interactions
- •Introduction
- •Backscattered Electrons
- •Secondary Yields
- •Stopping Powers
- •X-ray Ionization Cross Sections
- •Conclusions
- •References
- •Index
- •Reference List
- •Index
323 |
20 |
20.4 · The Need for an Iterative Qualitative and Quantitative Analysis Strategy
a |
|
|
|
|
|
|
|
|
|
IN100_20kV_residual |
|
|
80 000 |
|
|
|
|
|
|
|
|
||
|
|
|
|
|
IN100 |
|
|
|
IN100_20kV |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
E0 = 20 kev |
|
|
|
|
|
|
60 000 |
|
|
|
|
|
|
|
|
|
|
Counts |
40 000 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
20 000 |
|
|
|
|
|
|
|
|
|
|
|
00.0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
9.0 |
10.0 |
|
|
|
|
|
Photon energy (keV) |
|
|
|
|
|
|
b 10 000 |
IN100_20kV_residual |
|
|
|
IN100_20kV |
Counts
8 000 |
|
|
|
|
|
|
|
|
|
|
6 000 |
|
|
|
|
|
|
|
|
|
|
4 000 |
|
|
|
|
|
|
|
|
|
|
2 000 |
|
|
|
|
|
|
|
|
|
|
0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
9.0 |
10.0 |
0.0 |
||||||||||
|
|
|
|
Photon energy (keV) |
|
Note anomaly |
|
|
|
|
|
|
|
|
|
|
|
in background at TiK-M2,3 |
|
|
|
|
|
|
|
|
|
|
corresponding to V K-L2,3 |
|
|
|
. Fig. 20.9 Analysis of IN100 alloy fitting for Al, Ti, Cr, Co, Ni and Mo:
afull spectrum (blue) and residual spectrum after peak-fitting (red);
bexpanded view, note anomaly in background at the energy of Ti
K-M4,5 (4.931 keV), which closely corresponds to the energy of V K-L2,3 (4.952 keV)
. Table 20.9 Analysis of IN100 |
|
|
|
|
|
|
1st quantitative analysis |
2nd quantitative |
|
|
analysis |
|
|
|
Raw |
0.9944 ± 0.0011 |
1.0032 ± 0.0013 |
sum |
|
|
|
|
|
Al |
0.0559 ± 0.0007 |
0.0562 ± 0.0007 |
Ti |
0.0473 ± 0.0001 |
0.0474 ± 0.0001 |
V |
|
0.0110 ± 0.0002 |
Cr |
0.0981 ± 0.0002 |
0.0949 ± 0.0006 |
Co |
0.1551 ± 0.0003 |
0.1553 ± 0.0003 |
Ni |
0.6065 ± 0.0008 |
0.6069 ± 0.0008 |
Mo |
0.0315 ± 0.0002 |
0.0315 ± 0.0002 |
analysis (. Table 20.9), despite the severe interference from the Ti constituent which has a concentration more than four times higher.
20.4.2\ Analysis of a Stainless Steel
When is a Standard Not Suitable as a Peak-Fitting Reference? One of the great strengths of the k-ratio/matrix correction protocol is simplicity of the required standards. Pure elements can be used for most of the periodic table, and for those elements that are not in a suitable solid form at ambient temperature and at the low chamber pressure, stoichiometric binary compounds that are stable under the beam can be used. This is an excellent situation for the analyst, since it is generally not possible to have a multi-element standard that is homogeneous on the microscopic scale and similar in
\324 Chapter 20 · Quantitative Analysis: The SEM/EDS Elemental Microanalysis k-ratio Procedure for Bulk Specimens, Step-by-Step
a
Counts
b
Counts
10 000 |
|
|
|
IN100 |
|
|
|
|
|
IN100_20kV |
|
|
|
|
|
|
|
|
|
Residual[IN100_20kV] |
|||
|
|
|
|
E0 = 20 kev |
|
|
|
|
|
|
|
8 000 |
|
|
|
|
|
|
|
|
|
|
|
6 000 |
|
|
|
|
|
|
|
|
|
|
|
4 000 |
|
|
|
|
|
|
|
|
|
|
|
2 000 |
|
|
|
|
|
|
|
|
|
|
|
00.0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
9.0 |
10.0 |
|
|
|
|
|
|
|
Photon energy (keV) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
IN100_20kV_residual |
|
4 000 |
|
|
|
|
|
|
IN100 |
|
|
Residual[IN100_20kV]_withV-fit |
|
|
|
|
|
|
|
Residual without V |
|
|
|
||
|
|
|
|
|
|
|
Residual with V |
|
|
|
|
3 000 |
|
|
|
|
|
|
|
|
|
|
|
2 000 |
|
|
|
|
|
|
|
|
|
|
|
1 000 |
|
|
|
|
|
|
|
|
|
|
|
0 |
0.0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
9.0 |
10.0 |
|
|
|
|
|
|
Photon energy (keV) |
|
|
|
|
|
. Fig. 20.10 a IN100 superalloy, fitting for Al, Ti, V, Cr, Co, Ni, and Mo. b Comparison of fitting residuals with and without inclusion of V; the background anomaly is eliminated
composition to a particular unknown specimen. For many simple binary as well as more complex mixtures of elements, Nature favors heterogeneity on the microscale, and many combinations of elements tend to phase separate to produce chemically heterogeneous microstructures. However, there are important cases where microscopically homogeneous, multi-element compositions are available, such as minerals, glasses, and a few metal alloys. An example is NIST Standard Reference Material 479, an Fe-Cr-Ni alloy which is certified to be homogeneous on a microscopic scale. SRM 479 can serve as a standard for the analysis of another more complex stainless steel. . Figure 20.11 shows the spectrum of a type 316 stainless steel which the initial qualitative analysis shows
20 that in addition to Cr, Fe, and Ni also contains peaks for Si and Mo. While SRM 479 is an ideal standard for this analysis of Cr, Fe, and Ni, it is not suitable to provide peak-fitting references for Cr, Fe, and Ni because of the mutual interference of these peaks. Thus, pure elements for Cr, Fe, and Ni are used for the peak-fitting references, while SRM 479 is used as the standard, reducing the magnitude of the matrix corrections because of the close similarity of the unknown and standard compositions. When the analysis is performed, including elemental Si and Mo as references and standards,
the results given in . Table 20.10 (column 2) are obtained. Close examination of the residual spectrum reveals the peaks of the Mn K-family. When the analysis is repeated including Mn in the suite of fitted elements, the results given in
. Table 20.10 (column 3) are obtained with a concentration of Mn = 0.0154, and the residual spectrum no longer contains anomalous peaks, as shown in . Fig. 20.11c, d.
20.4.3\ Progressive Discovery: Repeated
Qualitative–Quantitative Analysis
Sequences
Complex unknowns may require several iterations of qualitative and quantitative analysis to discover all of the constituents. For such situations, the analytical total as well as the residual spectrum serve as powerful guides to reach a successful result. As an example, consider the spectrum of a monazite (a lanthanum-cerium phosphate mineral) shown in . Fig. 20.12a, b. The elements recognized in the first qualitative analysis stage are O, P, La, Ce (major) and Al, Si, Ca, and Th (minor). The first quantitative analysis round for these elements, with O calculated by stoichiometry, yielded
20.4 · The Need for an Iterative Qualitative and Quantitative Analysis Strategy
a
|
100 000 |
Stainless steel |
|
80 000 |
E0 = 20 kev |
Counts |
|
|
60 000 |
|
|
|
|
|
|
40 000 |
|
|
20 000 |
|
|
00.0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
|
|
|
|
|
Photon energy (keV) |
|
|
b |
|
|
|
|
|
|
|
|
6 000 |
|
|
|
|
|
|
Counts |
4 000 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2 000 |
|
|
|
|
|
|
|
0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
|
0.0 |
||||||
|
|
|
|
|
Photon energy (keV) |
|
|
c |
|
|
|
|
|
|
|
|
6 000 |
|
|
|
|
|
|
Counts |
4 000 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2 000 |
|
|
|
|
|
|
|
0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
|
0.0 |
||||||
|
|
|
|
|
Photon energy (keV) |
|
|
d |
|
|
|
|
|
|
|
|
4 000 |
|
|
|
|
|
|
Counts |
3 000 |
|
|
|
|
|
|
|
|
|
Stainless steel |
|
|
||
2 000 |
|
|
Residual without Mn |
|
|
||
|
|
|
|
|
|||
|
|
|
Residual with Mn |
|
|
||
|
|
|
|
|
|
||
|
1 000 |
|
|
|
|
|
|
|
0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
|
0.0 |
||||||
Photon energy (keV)
325 |
|
20 |
|
|
|
StainlessSteel_RR_20kV
StainlessSteel_RR_residual
7.08.0 9.0 10.0
StainlessSteel_RR_20kV
StainlessSteel_RR_residual
7.08.0 9.0 10.0
StainlessSteel_RR_20kV
Residual[StainlessSteel_RR_20kV]
7.08.0 9.0 10.0
Residual[StainlessSteel_RR_20kV]
StainlessSteel_RR_residual
7.0 |
8.0 |
9.0 |
10.0 |
. Fig. 20.11 a Stainless steel, fitting for Si, Cr, Fe, Ni, and Mo; residual in blue. b Expanded vertical scale, note detection of Mn. c Stainless steel, fitting for Si, Cr, Mn, Fe, Ni, and Mo; residual in blue. d Comparison of residuals with fitting for Mn (red) and without (blue)