1、BSI Standards PublicationBS ISO 17470:2014Microbeam analysis Electronprobe microanalysis Guidelines for qualitativepoint analysis by wavelengthdispersive X-ray spectrometryBS ISO 17470:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 17470:2014. Itsupersede
2、s BS ISO 17470:2004 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee CII/9, Microbeam analysis.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessary
3、provisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 84121 7ICS 71.040.99Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was publi
4、shed under the authority of theStandards Policy and Strategy Committee on 31 January 2014.Amendments issued since publicationDate Text affectedBS ISO 17470:2014 ISO 2014Microbeam analysis Electron probe microanalysis Guidelines for qualitative point analysis by wavelength dispersive X-ray spectromet
5、ryAnalyse par microfaisceaux Analyse par microsonde lectronique (Microsonde de Castaing) Lignes directrices pour lanalyse qualitative ponctuelle par spectromtrie de rayons X dispersion de longueur donde (WDX)INTERNATIONAL STANDARDISO17470Second edition2014-01-15Reference numberISO 17470:2014(E)BS IS
6、O 17470:2014ISO 17470:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or post
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8、so.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 17470:2014ISO 17470:2014(E) ISO 2014 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Abbreviated terms 25 Apparatus . 26 Procedure for identification . 26.1 General . 26.2
9、 Setting of analysis conditions . 26.3 Method for analysing an X-ray spectrum 46.4 Detection limit . 57 Test report . 6Annex A (informative) Example of the test report on qualitative analysis of a stainless steel sample by EPMA 7Bibliography .10BS ISO 17470:2014ISO 17470:2014(E)ForewordISO (the Inte
10、rnational 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
11、 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 s
12、tandardization.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 acco
13、rdance 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. Detai
14、ls 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 en
15、dorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee resp
16、onsible 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 reservedBS ISO 17470:2014ISO 17470:2014(E)Introduc
17、tionElectron 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 vB
18、S ISO 17470:2014BS ISO 17470:2014Microbeam analysis Electron probe microanalysis Guidelines for qualitative point analysis by wavelength dispersive X-ray spectrometry1 ScopeThis International Standard gives guidance for the identification of elements and the investigation of the presence of specific
19、 elements within a specific volume (on a m3scale) 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 referencesThe following documents, in whole or in part, a
20、re 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 micro
21、analysis Guidelines for the determination of experimental parameters for wavelength dispersive spectroscopy3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1higher order reflectionspeaks appearing at the diffracted angles corresponding to n = 2, 3
22、, 4Note 1 to entry: In WDS, X-rays are dispersed according to Braggs law, n = 2d sin, where is the X-ray wavelength, d is the interplanar spacing of the diffraction crystal, is the diffraction angle, and n is an integer. The higher order reflections are the peaks appearing at the diffracted angles c
23、orresponding to n = 2, 3, 43.2point analysisanalysis in which the primary beam is fixed, thus irradiating a selected region of a sample surfaceNote 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 stati
24、c beam or a raster area should be chosen such that relative X-ray intensities do not change when enlarging the analysis area.3.3Rowland circlecircle of focus along which the X-ray source, diffractor, and detector must all lie in order to satisfy the Bragg condition and obtain constructive interferen
25、ce3.4X-ray line tabletable of X-ray lines used for qualitative analysis by EPMANote 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
26、full width at half maximum (FWHM) of each peak, the interplanar spacings of the diffraction crystals, and the wavelengths of satellite peaks.INTERNATIONAL STANDARD ISO 17470:2014(E) ISO 2014 All rights reserved 1BS ISO 17470:2014ISO 17470:2014(E)4 Abbreviated termsEPMA electron probe microanalysisWD
27、S wavelength dispersive X-ray spectroscopy or spectrometry5 ApparatusCare 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
28、 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
29、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 app
30、ropriate 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 id
31、entification6.1 GeneralX-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 spectr
32、a.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 cond
33、itions6.2.1 Primary beamThe 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 f
34、or an overvoltage ratio equal to Napiers number (about 2,7). Taking into account the energy loss of the primary electrons, optimum excitation occurs at overvoltage ratios slightly greater than Napiers number. However, in the case of ultra-light elements and low energy X-rays from other elements (i.e
35、. 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 reservedBS ISO 17470:2
36、014ISO 17470:2014(E)ICiE EE CiU= ()= ()0cc1,71,71 (1)whereC is the constant;i is the primary beam current (A);E0is the primary beam energy (keV);Ecis the critical excitation energy (keV);U is the overvoltage ratio (E0/Ec).Note that as the primary beam energy increases, the intensity of generated X-r
37、ays become larger. Since the depth of the generation also increases, absorption of X-rays leaving the sample occurs, so the intensities of the detected X-rays do not necessarily become proportionally larger. In samples where absorption is particularly high, such as with light elements Be to F, it is
38、 recommended that a primary beam energy of 15 keV or less be used to reduce the depth of X-ray generation and hence the absorption effect. In the case of a thin film sample or a powder sample, primary beam energy should be determined by referring to 5.2 of ISO 14594:2003.The primary beam current sho
39、uld be also set in the range in which sample damage, sample contamination, and saturation of the X-ray detectors are minimized.6.2.2 X-ray spectrometer6.2.2.1 Selection of diffraction crystalsThe diffraction crystals selected should be capable of detecting the intended elements, with a maximum peak-
40、to-background ratio and peak resolution, but with minimum interference from peaks of other elements in the sample. Since it is not always possible to optimize all of these parameters simultaneously, the analyst should select the diffraction crystal that will provide the best compromise for the speci
41、fic analysis requirements.6.2.2.2 Scanning speedA scanning speed should be selected that will enable the detection of the anticipated elements at their anticipated concentrations.NOTE 1 The scanning speed of a digitally scanned spectrometer is defined by the number of steps, the length of a step, an
42、d the sampling time per step. The number of steps should be high enough and the length of a step should be short enough to sufficiently resolve the shape and height of the detected peaks. In practice, a measured peak should contain a minimum of five data points.NOTE 2 When the signal from the analys
43、ed element is low relative to the background, a slower scanning speed should be used.6.2.2.3 Pulse height analyserAs peaks of higher order reflections, originating from other constituents, appear in WDS spectra, some uncertainty can arise about the presence of elements having a peak in the same posi
44、tion as one of these higher order reflections. In this case, the higher order reflection can be suppressed by using the discrimination of a pulse height analyser. Care should be taken in selecting a proper discrimination window size and baseline level to avoid unnecessary loss of peak intensity from
45、 the element of interest. The analyst should confirm proper transmission of signal by analysing an appropriate reference material and comparing the peak height and shape both with and without pulse height discrimination. ISO 2014 All rights reserved 3BS ISO 17470:2014ISO 17470:2014(E)6.3 Method for
46、analysing an X-ray spectrum6.3.1 Recognition of a peakRecognition of a peak is done by reference to both its width and its height. In spectra, the FWHM of the peak should be nearly equal to the FWHM of the same peak in the X-ray line table or equal to the same peak measured from a laboratory standar
47、d. Narrower peaks can be noise spikes and can usually be disregarded. The peak height should be determined by the difference between the peak intensity and the background intensity. The background intensity should be determined in accordance with 6.3.3 of ISO 14594:2003.In the case where the peak in
48、tensity approaches the background level, if a peak is found by visual examination, the probability of the presence of the peak is given as follows:If NN NPB B2, then the confidence level is 97,7 %NN NPB B3, then the confidence level is 99,9 %whereNPis the peak intensity, expressed in X-ray counts;NB
49、is the mean background intensity in the vicinity of the peak, expressed in X-ray counts;NBis the standard deviation of the background intensity in the vicinity of the peak.The above expressions are explained as follows.As the distribution of the X-ray counts can be approximated by Gaussian distribution, the standard deviation of the background X-ray counts is given by NB. Therefore, if the height of a suspected peak (in counts) exceeds NNBB+2 or NNBB+3 , there is a 97,7 % or 99,9 % probability, respectively, that th
