Microbeam analysis — Electron probe microanalysis — Guidelines for qualitative point analysis by wavelength dispersive X-ray spectrometry

ISO 17470:2014 gives guidance for the identification of elements and the investigation of the presence of specific elements within a specific volume (on a μm3 scale) contained in a specimen, by analysing X-ray spectra obtained using wavelength dispersive X-ray spectrometers on an electron probe microanalyser or on a scanning electron microscope.

Analyse par microfaisceaux — Analyse par microsonde électronique (Microsonde de Castaing) — Lignes directrices pour l'analyse qualitative ponctuelle par spectrométrie de rayons X à dispersion de longueur d'onde (WDX)

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Status
Published
Publication Date
05-Jan-2014
Current Stage
9093 - International Standard confirmed
Start Date
06-Jun-2019
Completion Date
06-Jun-2019
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INTERNATIONAL ISO
STANDARD 17470
Second edition
2014-01-15
Microbeam analysis — Electron
probe microanalysis — Guidelines
for qualitative point analysis
by wavelength dispersive X-ray
spectrometry
Analyse par microfaisceaux — Analyse par microsonde électronique
(Microsonde de Castaing) — Lignes directrices pour l’analyse
qualitative ponctuelle par spectrométrie de rayons X à dispersion de
longueur d’onde (WDX)
Reference number
ISO 17470:2014(E)
ISO 2014
---------------------- Page: 1 ----------------------
ISO 17470:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

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Published in Switzerland
ii © ISO 2014 – All rights reserved
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ISO 17470:2014(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviated terms .............................................................................................................................................................................................. 2

5 Apparatus ..................................................................................................................................................................................................................... 2

6 Procedure for identification ..................................................................................................................................................................... 2

6.1 General ........................................................................................................................................................................................................... 2

6.2 Setting of analysis conditions ..................................................................................................................................................... 2

6.3 Method for analysing an X-ray spectrum.......................................................................................................................... 4

6.4 Detection limit ......................................................................................................................................................................................... 5

7 Test report ................................................................................................................................................................................................................... 6

Annex A (informative) Example of the test report on qualitative analysis of a stainless steel

sample by EPMA .................................................................................................................................................................................................... 7

Bibliography .............................................................................................................................................................................................................................10

© ISO 2014 – All rights reserved iii
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ISO 17470:2014(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 202, Microbeam analysis, Subcommittee SC 2,

Electron probe microanalysis.

This second edition cancels and replaces the first edition (ISO 17470:2004), of which it constitutes a

minor revision.
iv © ISO 2014 – All rights reserved
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ISO 17470:2014(E)
Introduction

Electron probe microanalysis is used to qualitatively identify the elements present in a specimen on a

micrometric scale. It is necessary to specify the measurement conditions and identification method in

order to avoid reporting erroneous or inconsistent results.
© ISO 2014 – All rights reserved v
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INTERNATIONAL STANDARD ISO 17470:2014(E)
Microbeam analysis — Electron probe microanalysis —
Guidelines for qualitative point analysis by wavelength
dispersive X-ray spectrometry
1 Scope

This International Standard gives guidance for the identification of elements and the investigation of

the presence of specific elements within a specific volume (on a μm scale) contained in a specimen,

by analysing X-ray spectra obtained using wavelength dispersive X-ray spectrometers on an electron

probe microanalyser or on a scanning electron microscope.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 14594:2003, Microbeam analysis — Electron probe microanalysis — Guidelines for the determination

of experimental parameters for wavelength dispersive spectroscopy
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
higher order reflections
peaks appearing at the diffracted angles corresponding to n = 2, 3, 4…

Note 1 to entry: In WDS, X-rays are dispersed according to Bragg’s law, nλ = 2d sinθ, where λ is the X-ray wavelength,

d is the interplanar spacing of the diffraction crystal, θ is the diffraction angle, and n is an integer. The higher

order reflections are the peaks appearing at the diffracted angles corresponding to n = 2, 3, 4…

3.2
point analysis

analysis in which the primary beam is fixed, thus irradiating a selected region of a sample surface

Note 1 to entry: The method where the primary beam rapidly scans over a very small region on the sample surface

is also included. The maximum size of a static beam or a raster area should be chosen such that relative X-ray

intensities do not change when enlarging the analysis area.
3.3
Rowland circle

circle of focus along which the X-ray source, diffractor,

and detector must all lie in order to satisfy the Bragg condition and obtain constructive interference

3.4
X-ray line table
table of X-ray lines used for qualitative analysis by EPMA

Note 1 to entry: The X-ray line table for qualitative analysis by EPMA lists the wavelengths of K-, L-, and, M-lines

for the elements observed on each diffraction crystal. It can also list their relative intensities, the full width at

half maximum (FWHM) of each peak, the interplanar spacings of the diffraction crystals, and the wavelengths of

satellite peaks.
© ISO 2014 – All rights reserved 1
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ISO 17470:2014(E)
4 Abbreviated terms
EPMA electron probe microanalysis
WDS wavelength dispersive X-ray spectroscopy or spectrometry
5 Apparatus

Care should be taken to ensure the instrument is performing satisfactorily. In particular, that the

electron column is correctly aligned, the beam current is stable, the accelerating voltage and beam

current are appropriate for the sample, the sample surface is prepared suitably for quantitative analysis,

the working distance is correct, and the spectrometer crystals and X-ray counters are calibrated and

aligned so that the spectrum exhibits X-ray peaks with appropriate intensities and shapes.

NOTE 1 Operators should be aware that parameters such as peak position, relative peak heights, peak

resolutions, FWHM values, etc. can vary slightly from instrument to instrument, and also from sample to sample.

This can be largely corrected for by periodically comparing values with an appropriate X-ray line table and data

from appropriate laboratory reference materials.

NOTE 2 If the sample surface is not planar or polished or perpendicular to the beam, care should be taken in

determining the actual value of the local take-off angle and the ability of the spectrometer to properly analyse

this kind of sample.
6 Procedure for identification
6.1 General

X-ray spectra are obtained by directing the incident electron beam at the point to be analysed on the

sample surface and scanning the X-ray spectrometers over a specified wavelength range. Qualitative

analysis is performed by identifying each peak in the resulting X-ray spectra.

It is necessary to verify whether the peak identified interferes with a peak resulting from another

element. Particular care is needed for possible higher order reflections originating from other elements

in the sample, usually, but not always, at higher concentrations.
6.2 Setting of analysis conditions
6.2.1 Primary beam

The primary beam energy should be higher than the X-ray excitation energies of analysed elements,

but low enough to minimize sample damage, contamination of the sample, and saturation of the X-ray

detectors.

NOTE 1 The Bethe inner shell ionization cross section has a maximum for an overvoltage ratio equal to

Napier’s number (about 2,7). Taking into account the energy loss of the primary electrons, optimum excitation

occurs at overvoltage ratios slightly greater than Napier’s number. However, in the case of ultra-light elements

and low energy X-rays from other elements (i.e. low energy L- and M-lines), absorption from surface layers can

significantly affect the optimum overvoltage causing it to be substantially higher than 2,7.

NOTE 2 The intensity of a generated characteristic X-ray, I, is given approximately by Formula (1):

2 © ISO 2014 – All rights reserved
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ISO 17470:2014(E)
1,7
1,7
 
IC=×iE −EE =×Ci()U −1 (1)
0c c
 
where
C is the constant;
i is the primary beam current (A);
E is the primary beam energy (keV);
E is the critical excitation energy (keV);
U is the overvoltage ratio (E /E ).
0 c
Note that as the primary beam energy increases, the intensity of generated X
...

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