Overview
EN ISO 21068-4:2024 - Chemical analysis of raw materials and refractory products containing silicon-carbide, silicon-nitride, silicon-oxynitride and sialon - Part 4: XRD methods (ISO 21068‑4:2024) defines X‑ray diffraction procedures for identifying and quantifying mineralogical phases in nitride and oxy‑nitride bonded silicon carbide refractory products. The standard specifies sample preparation, instrument requirements for a Bragg–Brentano diffractometer, measurement parameters, and quantitative refinement tied to the sample’s total nitrogen content.
Key topics and technical requirements
- Scope: Qualitative and quantitative XRD analysis of phases typically present in nitride/oxy‑nitride bonded SiC refractories.
- Target phases for quantification: α‑Si3N4, β‑Si3N4, Si2ON2, AlN, and β’‑SiAlON.
- Instrument & optics:
- Bragg–Brentano geometry with Cu X‑ray tube (40 kV, 20–45 mA).
- Primary and secondary beam monochromation (filters, graphite monochromator or equivalent).
- Goniometer uncertainty ≤ 0.5° (95 % confidence).
- Suggested slit settings: divergence slit 1°, receiving slit ≤ 0.2 mm, scatter slit ≤ 1°, primary Soller ≤ 2.5°.
- Sample preparation:
- Grind to pass a 150 µm sieve; avoid excessive grinding (to limit amorphous surface formation on Si‑bearing phases).
- Press powder uniformly into a flat sample holder cavity; use back‑fill holders to reduce preferred orientation. Cavity depth must exceed the critical depth for CuKα radiation.
- Measuring parameters:
- Scan range 2θ: start 10°; end 70° (or 130° when β‑SiAlON determination required).
- Step-size 2θ 0.02° or continuous scan; integration time ~4 s.
- Quantitative refinement: Procedures incorporate the total nitrogen content of the sample (ISO 21068‑3 is referenced for nitrogen analysis).
Applications and users
This part of ISO 21068 is designed for:
- Quality control laboratories in refractory manufacturing.
- R&D teams developing silicon‑nitride/SiAlON bonded SiC refractories.
- Material suppliers verifying phase composition of raw materials.
- Third‑party testing and certification bodies performing compliance and acceptance testing.
Practical uses include phase composition reporting, process control, failure analysis, and materials development where accurate phase quantification (including nitrogen‑based refinement) is required.
Related standards
- ISO 21068‑1 - General information and sample preparation
- ISO 21068‑3 - Determination of nitrogen, oxygen and metallic/oxidic constituents (used for nitrogen data)
- ISO 5022, ISO 8656‑1 - Sampling of shaped and unshaped refractory products
- ISO 10081‑4 - Classification of dense shaped refractory products
Keywords: EN ISO 21068-4:2024, XRD methods, Bragg‑Brentano diffractometer, silicon carbide refractory, silicon nitride, SiAlON, quantitative XRD, sample preparation, total nitrogen.
