Round robin test PT LS BAM-5.5-2021 “Particle size determination of ceramic powders using the laser scattered light method according to ISO 13320:2020”

As in the previous rounds (2014, 2016, 2019), employees of FGK test laboratory were able to determine the particle sizes of three ceramic powders 100% correctly in 2021.
The “Mastersizer 3000” laser granulometer from Malvern GmbH (now Malvern Panalytical GmbH) was used. The analyses followed ISO 13320:2020 and the additional specifications of the ring test organizer (Federal Institute for Materials Research and Testing, Berlin).
All powders were analyzed in the dispersed state using the Mie evaluation procedure.
The range of materials previously analyzed in connection with interlaboratory comparisons included glass spheres and ballotini, “ceramic spheres,” and powders of alumina, quartz (silicon dioxide), silica glass, zirconium silicate, silicon carbide, and barium titanate with spherical and irregular grain shapes.
The laser scattering light method (also known as laser granulometry or laser diffraction analysis) is based on the measurement of the different scattering patterns produced by different sized particles when scattering monochromatic light, which is mainly produced by lasers. The laser granulometer “Mastersizer 3000” used at FGK uses monochromatic light of two wavelengths (“red” light with a wavelength of 632.8 nm, generated by a He-Ne laser, or “blue” light with a wavelength of 470 nm, generated by an LED). With the help of optical models (Mie theory, Fraunhofer approximation), corresponding particle size distributions of laser scattered light equivalent spheres (corresponding to spherical particles) are calculated from the generated scattering patterns.
At FGK test laboratory, the laser scattered light method is one of the frequently used physical measurement methods and is also accredited for determining the particle size distribution of ceramic powders in accordance with DIN EN 725-5:2007-04. An additional accreditation according to ISO 13320:2020 (Particle size analysis – Laser diffraction methods) is in preparation.
Depending on the material and particle size, the available accessories allow particle size determination of powdery solids in dry or predispersed state. The so-called wet dispersion is carried out at FGK mainly with deionized water. For water-soluble samples, alternative dispersing media such as ethanol or (iso-)propanol are routinely available. In individual cases, other dispersing media can be used.
According to the measuring instrument manufacturer, particle size distributions in the particle size range between min. 10 nm (for dry dispersion: 100 nm) and max. 3480 µm can be measured.
The measurement reports documented at FGK test reports include the respective volume fractions and cumulative volumes as a function of particle size, as well as tabular information on the particle diameters corresponding to the respective percentiles (e.g. D10, D50, D90) of the distribution sum of the volume-weighted particle size distribution.