ISO 25498:2018

INTERNATIONAL ISO
STANDARD 25498
Second edition
2018-03
Microbeam analysis — Analytical
electron microscopy — Selected area
electron diffraction analysis using a
transmission electron microscope
Analyse par microfaisceaux — Microscopie électronique analytique
— Analyse par diffraction par sélection d'aire au moyen d'un
microscope électronique en transmission
Reference number
©
ISO 2018
© ISO 2018
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
4.1 General . 3
4.2 Spot diffraction pattern . 3
4.3 Kikuchi pattern . 6
4.4 Polycrystalline specimen . 7
5 Reference materials . 7
6 Equipment . 8
7 Specimens . 8
8 Experimental procedure . 8
8.1 Instrument preparation . 8
8.2 Procedure for acquirement of selected area electron diffraction patterns . 9
8.3 Determination of diffraction constant, Lλ .12
9 Measurement and solution of the SAED patterns .13
9.1 Selection of the basic parallelogram .13
9.2 Indexing diffraction spots .15
10 180° ambiguity .16
11 Uncertainty estimation.16
11.1 Factors affecting accuracy .16
11.2 Calibration with a reference material .17
Annex A (informative) Interplanar spacing .18
Annex B (informative) Spot diffraction patterns of single crystals for BCC, FCC and HCP
[ ]
structure 7 .19
Bibliography .38
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
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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).
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URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 202, Microbeam analysis, Subcommittee
SC 3, Analytical electron microscopy.
This second edition cancels and replaces the first edition (ISO 25498:2010), which has been technically
revised.
The main changes to the previous edition are as follows:
— the foreword has been revised;
— the introduction has been revised;
— the scope has been revised;
— the figure of Ewald construction has been deleted;
— the terms and definition of terminological entries 3.1, 3.2, 3.10, 3.11, 3.12, 3.13 and 3.14 have
been added;
— the subclause 4.1 has been added;
— Clause 5 has been revised;
— Clauses 4, 6, 7, and 10 and subclauses 8.1.5, 8.1.6, 8.2.1, 8.2.2, 8.2.4, 8.2.7, 8.2.8, 8.2.11 and 9.1.2 have
been editorially revised;
— the subclause 9.2.5 has been added;
— all formulae have been renumbered;
— Annex A has been revised;
— the subclause B.1 has been revised;
iv © ISO 2018 – All rights reserved

— the figures have been modified;
— the bibliography has been updated.
Introduction
Electron diffraction techniques are widely used in transmission electron microscopy (TEM) studies.
Applications include phase identification, determination of the crystallographic lattice type and
lattice parameters, crystal orientation and the orientation relationship between two phases, phase
transformations, habit planes and defects, twins and interfaces, as well as studies of preferred crystal
orientations (texture). While several complementary techniques have been developed, for example
microdiffraction, convergent beam diffraction and reflected diffraction, the selected area electron
diffraction (SAED) technique is the most frequently employed.
This technique allows direct analysis of small areas on thin specimens from a variety of crystalline
substances. It is routinely performed on most of TEM in the world. The SAED is also a supplementary
technique for acquisition of high resolution images, microdiffraction or convergent beam diffraction
studies. The information generated is widely applied in the studies for the development of new
materials, improving structure and/or properties of various materials as well as for inspection and
quality control purpose.
The basic principle of the SAED method is described in this document. The experimental procedure
for the acquirement of SAED patterns, indexing of the diffraction patterns and determination of the
diffraction constant are specified. ISO 25498 is intended for use or reference as technical regulation for
transmission electron microscopy.
vi © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 25498:2018(E)
Microbeam analysis — Analytical electron microscopy
— Selected area electron diffraction analysis using a
transmission electron microscope
1 Scope
This document specifies the method of selected area electron diffraction (SAED) analysis using a
transmission electron microscope (TEM) to analyse thin crystalline specimens. This document applies
to test areas of micrometres and sub-micrometres in size. The minimum diameter of the selected area
in a specimen which can be analysed by this method is restricted by the spherical aberration coefficient
of the objective lens of the microscope and approaches several hundred nanometres for a modern TEM.
When the size of an analysed specimen area is smaller than that restriction, this document can also
be used for the analysis procedure. But, because of the effect of spherical aberration, some of the
diffraction information in the pattern can be generated from outside of the area defined by the selected
area aperture. In such cases, the use of microdiffraction (nano-beam diffraction) or convergent beam
electron diffraction, where available, might be preferred.
This document is applicable to the acquisition of SAED patterns from crystalline specimens, indexing
the patterns and calibration of the diffraction constant.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
Miller index
notation system for crystallographic planes and directions in crystals, in which a set of lattice planes or
directions is described by three axes coordinate
3.2
Miller-Bravais index
notation system for crystallographic planes and directions in hexagonal crystals, in which a set of
lattice planes or directions is described by four axes coordinate
3.3
(h k l)
Miller indices (3.1) of a specific set of crystallographic planes
3.4
{hkl}
Miller indices (3.1) which denote a family of crystallographic planes
3.5
[uvw]
Miller indices (3.1) of a specific crystallographic direction or a zone axis
3.6
interplanar spacing
d
hkl
perpendicular distance between consecutive planes of the crystallographic plane set (h k l) (3.3)
3.7
(uvw)*
notation for a set of planes in the reciprocal lattice
Note 1 to entry: The normal of the reciprocal plane (uvw)* is parallel to the crystallographic zone axis [uvw] (3.5).
3.8
reciprocal vector
g
hkl
vector in the reciprocal lattice
Note 1 to entry: The reciprocal vector, g is normal to the crystallographic plane (h k
...