Overview
ISO 17470:2014 provides guidance for qualitative point analysis by wavelength dispersive X‑ray spectrometry (WDS/WDX) using an electron probe microanalyser (EPMA) or a scanning electron microscope. The standard focuses on identifying which elements are present within a defined micrometric volume (μm3 scale) by analysing WDX spectra, and on documenting the measurement conditions and identification method to avoid inconsistent or erroneous results.
Key topics and technical requirements
- Scope and purpose: Guidance for element identification and investigation of specific elements at micrometric scale using EPMA/WDX.
- Apparatus and instrument performance: Ensure correct electron column alignment, stable beam current, suitable accelerating voltage, calibrated spectrometer crystals and X‑ray counters, and appropriate sample surface preparation.
- Primary beam settings: Select beam energy above excitation energies but low enough to minimize damage, contamination and detector saturation. For very light elements (Be to F), a primary beam energy of 15 keV or less is recommended to reduce absorption effects.
- Spectrometer configuration:
- Diffraction crystal selection to maximize peak‑to‑background and resolution while minimizing interferences.
- Scanning speed should give sufficient data points per peak (practically, measured peaks should contain at least five data points).
- Pulse height analyser discrimination can suppress higher‑order reflections but must be validated with reference materials to avoid loss of signal.
- Spectrum analysis and peak recognition:
- Use reliable X‑ray line tables or laboratory standards to identify peaks.
- Evaluate peaks by FWHM and peak height above background. Peaks exceeding background by 2σ or 3σ correspond to approximate confidence levels of 97.7% and 99.9%, respectively.
- Check for higher‑order reflections, overlapping peaks, absorption/fluorescence effects and possible contamination from sample preparation.
- Reporting: The standard specifies information to include in a test report; Annex A gives an example (stainless steel).
Applications
- Qualitative element identification in microstructures, inclusions, coatings, thin films, ceramics, metals and geological samples.
- Failure analysis, contamination/source tracing, quality control and research where spatially resolved elemental presence at the micrometer scale is required.
- Validating sample preparation and EPMA/WDS operating procedures for laboratories performing microbeam analysis.
Who should use this standard
- Materials scientists, metallurgists, geoscientists, semiconductor and thin‑film engineers
- Electron microscopy and microanalysis laboratory managers and technicians
- Quality assurance personnel and researchers using EPMA/WDS for qualitative point analyses
Related standards
- ISO 14594:2003 - Microbeam analysis - EPMA - Guidelines for determination of experimental parameters for WDS (normative reference cited in ISO 17470:2014).
Open preview (PDF)Microbeam analysis — Electron probe microanalysis — Guidelines for qualitative point analysis by wavelength dispersive X-ray spectrometry
