ISO 20720:2018

Microbeam analysis - Methods of specimen preparation for analysis of general powders using WDS and EDS

This document specifies specimen preparation methods for the analysis of particles in powders using energy-dispersive spectrometers (EDS) or wavelength-dispersive spectrometers (WDS) installed on an EPMA or SEM. The preparation methods for powder particle analysis are classified by the analytical purpose and the particle size. This document applies to inorganic particles larger than 100 nm and smaller than 100 µm in diameter. It applies only to analysis of "general" powders, which means that it excludes procedures for special applications such as forensic or trace analysis.

Analyse par microfaisceaux — Méthodes de préparation des échantillons pour l’analyse des particules

General Information

• Status: Published
• Publication Date: 17-Oct-2018
• ICS: 71.040.99 - Other standards related to analytical chemistry
• Technical Committee: ISO/TC 202 - Microbeam analysis
• Drafting Committee: ISO/TC 202 - Microbeam analysis
• Current Stage: 9093 - International Standard confirmed
• Start Date: 30-Apr-2024
• Completion Date: 13-Dec-2025

Overview

ISO 20720:2018 - Microbeam analysis: Methods of specimen preparation for analysis of general powders using WDS and EDS - defines standardized specimen preparation methods for particle analysis by energy-dispersive (EDS) and wavelength-dispersive (WDS) X‑ray spectrometry on EPMA or SEM platforms. It covers inorganic powder particles between 100 nm and 100 µm diameter and classifies preparation procedures by analytical purpose and particle size. Special-application procedures (forensic or trace analysis) are excluded.

Key topics and technical requirements

• Scope and classification
  • Applies to general inorganic powders (100 nm–100 µm), with methods chosen according to particle size and analysis goal (surface, whole-particle, cross‑section, statistical).
• Specimen preparation methods
  • Surface/whole-particle: sprinkling onto conductive tape/substrate, drying drops of suspension, suction filtration, tablet pressing.
  • Cross‑section: embedding in resin and polishing, microtomy, focused ion beam (FIB) or broad argon ion sectioning.
• Sample handling details
  • Guidance on avoiding particle agglomeration (ultrasonication, centrifugation), fixation of small quantities, and removal of poorly adhered material (air duster, tapping).
  • Use of silver or tin flakes in tablet pressing for individual particles (note: sulfides can react with silver; tin is recommended in such cases).
• Charge mitigation and conductivity
  • Electrical conductivity processing via vacuum deposition or ion plating; choice depends on analysis purpose (see ISO 22489:2016).
  • Protective conductive/thermal layers (Au, Pt) and electron‑beam induced deposition for beam-sensitive particles.
• Analytical considerations
  • Effects of press pressure, particle packing and size on X‑ray intensity are illustrated in Annexes A and B. Examples show X‑ray strength dependence on tablet‑forming pressure and particle size (recommendations include grinding to 0.1–1 µm to improve filling density and noting typical tablet pressures used in examples).
  • Cautions when X‑ray generation volume exceeds particle dimensions - impacts quantitative interpretation.

Applications and practical value

• Standardizes sample‑preparation workflows for:
  • Materials characterization and failure analysis (ceramics, oxides, minerals, catalysts).
  • Quality control in powder manufacturing and processing.
  • Research labs performing EPMA/SEM elemental mapping and point analysis of powders.
• Practical benefits:
  • Improves reproducibility and comparability of WDS/EDS results.
  • Reduces artefacts from charging, agglomeration, or insufficient packing.
  • Guides choice of method for whole‑particle vs cross‑sectional analysis and for statistical studies of particle size/distribution.

Who should use this standard

• Microbeam analysts, SEM/EPMA operators, materials scientists, laboratory managers, and sample‑preparation technicians involved in powder analysis.

Related standards

• ISO 14594:2014 - EPMA experimental parameters (WDS)
• ISO 22489:2016 - Conductivity processing and quantitative point analysis guidance

Keywords: ISO 20720:2018, microbeam analysis, specimen preparation, powder analysis, EDS, WDS, EPMA, SEM, particle analysis, sample prep.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 20720
First edition
2018-10
Microbeam analysis — Methods of
specimen preparation for analysis of
general powders using WDS and EDS
Analyse par microfaisceaux — Méthodes de préparation des
échantillons pour l’analyse des particules
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
[1]
5 Analytical purposes and methods of specimen preparation for particle analysis .1
5.1 Methods of specimen preparation for particle analysis . 1
5.2 Description of preparation methods . 2
5.2.1 Analysis of whole particles or surface of particles . 2
5.2.2 Analysis of cross-section of particles . 4
5.3 Choosing preparation methods . 5
6 Electric conductivity processing . 6
Annex A (informative) Examples of X-ray strength dependency on tablet-forming pressure .7
Annex B (informative) Example of X-ray strength dependency on tablet-forming particle size .8
Bibliography . 9
Foreword
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iv © ISO 2018 – All rights reserved

Introduction
Although there are many applications of electron probe microanalysis (EPMA) and scanning electron
microscopy (SEM) for powder analysis, there are some difficulties, especially in the case of individual
particle analysis, as follows:
(a) the prevention of agglomeration of particles during preparation of the specimen;
(b) the fixation of specimens, especially when there is a small amount of tiny particles, either for
surface analysis or cross-section analysis;
(c) the cross-section preparation in the case of small particles with core-shell structures;
(d) the protection of particle surfaces from damage by electron beam irradiation in cases where the
surfaces of particles are sensitive;
(e) the counteraction of charging of the specimen under electron radiation to prevent the powder from
scattering or dispersing due to electrical repulsion;
(f) the interpretation of qualitative and/or quantitative analysis results when the X-ray generation
volume is larger than that of the particles.
Even in the case of elemental compositional analysis of a powder, the specimen preparation can
affect the results of analysis, because the roughness and/or void space within a particle aggregate or
agglomerate can impact X-ray intensity.
To cope with these difficulties, the standardization of specimen preparation for particle analysis is very
important.
INTERNATIONAL STANDARD ISO 20720:2018(E)
Microbeam analysis — Methods of specimen preparation
for analysis of general powders using WDS and EDS
1 Scope
This document specifies specimen preparation methods for the analysis of particles in powders using
energy-dispersive spectrometers (EDS) or wavelength-dispersive spectrometers (WDS) installed on
an EPMA or SEM. The preparation methods for powder particle analysis are classified by the analytical
purpose and the particle size.
This document applies to inorganic particles larger than 100 nm and smaller than 100 µm in diameter.
It applies only to analysis of “general” powders, which means that it excludes procedures for special
applications such as forensic or trace analysis.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Abbreviated terms
EDS energy-dispersive X-ray spectroscopy/spectrometry
EPMA electron probe microanalysis/electron probe microanalyzer
SEM scanning electron microscopy/scanning electron microscope
WDS wavelength-dispersive X-ray spectroscopy/spectrometry/spectrometer
5 Analytical purposes and methods of specimen preparation for particle
[1]
analysis
5.1 Methods of specimen preparation for particle analysis
The following methods of specimen preparation are widely used for particle analysis (see Figure 1).
The specific procedure is indicated in 5.2.
This list is not comprehensive and does not preclude the use of other specimen preparation methods for
particle analysis that can be more appropriate in some cases.
Figure 1 — Methods of specimen preparation for particle analysis
5.2 Description of preparation methods
5.2.1 Analysis of whole
...