SIST EN ISO 21821:2023 PDF

Overview

EN ISO 21821:2022 specifies a standardized test method for determining the densification properties of ceramic powders during natural (pressure-free) sintering. Intended for fine/advanced ceramics, the standard covers measurement of dimensional and mass changes of cylindrical powder compacts that are sintered at high temperature without external pressure. It applies to oxides, oxide mixtures, solid solutions and to non-oxides (e.g., carbides, nitrides) when sintered under vacuum or inert gas (≤ 1 bar). It explicitly excludes materials that require pressure-assisted sintering (HP, HIP, GPS, SPS).

Key Topics and Requirements

• Scope and applicability: natural (pressureless) sintering for granulated or ungranulated powders; inorganic sintering additives allowed if reported.
• Measured quantities: mass, diameter, height, volume and apparent density measured before and after sintering to quantify shrinkage and densification.
• Result representation: relative variations (mass, diameter, height, volume, density) and densification curves (e.g., relative density vs sintering temperature for given compacting pressures).
• Apparatus requirements:
  • Cylindrical die and punches (floating or single-acting) for producing test compacts (specified diameter and height‑to‑diameter ratios).
  • Furnace with hot zone uniformity (max ±10 °C variation) and heating-rate control (within ±2 °C/h); capability for vacuum or controlled inert atmosphere when required.
  • Press (force precision ±2 %), balance (resolution ±0.001 g), micrometer (resolution ±0.01 mm, per ISO 3611).
• Procedure elements: compaction method, selection of test temperatures, thermal cycle (heating rate, dwell), measurement method, sampling and reporting.
• Limitations: not applicable to ceramics that only densify under pressure-assisted techniques.

Applications and Users

EN ISO 21821:2022 is used to:

• Evaluate sinterability and densification behavior of ceramic powder formulations during process development.
• Compare powder batches, sintering schedules and effects of additives on shrinkage and final density.
• Support quality control in manufacturing of advanced technical ceramics (electronic ceramics, structural ceramics, wear-resistant components). Primary users:
• Materials scientists and ceramic engineers
• R&D labs and production quality teams
• Testing laboratories (ISO/IEC 17025 accredited)
• Powder suppliers and formulators

Related Standards

• ISO 17172 - Determination of compaction properties of ceramic powders
• ISO 3611 - Micrometers for external measurements
• ISO/IEC 17025 - Laboratory competence and calibration
• EN ISO 21821:2022 supersedes EN 725-11:2006

EN ISO 21821 provides a reproducible framework for measuring densification during natural sintering and producing comparable densification curves and reports useful for R&D, process optimization and conformity assessment of fine ceramics.