CCQM-K144 Trace elements in alumina powder

Main text Aluminum oxide (Al 2 O 3 ), commonly referred to as alumina, is extensively used in a variety of applications as a fundamental material for ceramics, catalyst substrates, ingredients in cosmetics, or media in chromatography. High purity alumina, in particular, plays a crucial role in the display and semiconductor industries. Trace elements such as iron (Fe), magnesium (Mg) and silicon (Si) in high-purity alumina can significantly affect the material's properties such as optical transparency and mechanical strength, potentially degrading the quality of final products. Therefore, the accurate measurements of trace elements in alumina are important for the relevant industries. Despite the importance, there had been no CCQM (Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology) IAWG (Inorganic Analysis Working Group) comparison studies on such advanced materials since 2008. Thus, a Key Comparison was initiated to address the current and future CMCs (Calibration and Measurement Capabilities) for category "9. Advanced materials" in "List of Amount of Substance Categories" of CCQM CMCs particularly concerning "Difficult to dissolve metals" of "Matrix challenges" in the IAWG Core Capability table. Then, KRISS proposed a comparison for measurements of elemental impurities in alumina powder and CCQM IAWG approved the Key Comparison (KC), CCQM-K144 Trace elements in alumina powder, in parallel with CCQM-P182. There are four participants, JSI (Slovenia), KRISS (Republic of Korea), NIM (China), UNIIM (Russia), in CCQM-K144. Participants measured the mass fractions, expressed in mg/kg, of iron (Fe), magnesium (Mg), and silicon (Si) in high purity alumina powder. Participants were free to choose any appropriate methods based on their measurement procedures, considering complete dissolution of the alumina powder, if required. Various measurement procedures including Inductively Coupled Plasma Mass Spectrometry (ICP-MS) with standard addition (SA) or isotope dilution (ID) calibration approaches, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) with standard addition (SA) following sample dissolution were employed by the participants. Additionally, Instrumental Neutron Activation Analysis with k 0 -method ( k 0 -INAA) was also implemented for Fe without needing to dissolve the alumina by one participant demonstrating equivalence between measurement results regardless of sample dissolution. After extensive discussions in the IAWG, the Key Comparison Reference Values (KCRVs) and Degrees of Equivalence (DoEs) for all three measurands were calculated using the NIST Decision Tree (NDT) for Key Comparisons (https://decisiontree.nist.gov). The consensus estimates and standard uncertainties for mass fractions of Fe, Mg, and Si were calculated based on the statistical model, "Hierarchical Gauss-Gauss", recommended in the NDT application and were then selected as the candidate KCRVs and their standard uncertainties. The values were w (Fe) = 2.332 mg/kg ( u (Fe) = 0.109 mg/kg), w(Mg) = 2.341 mg/kg (u(Mg)= 0.307 mg/kg) and w(Si) = 12.22 mg/kg (u(Si) = 0.83 mg/kg), respectively. Successful participation in CCQM-K144 directly demonstrates each participant's measurement capabilities in determining mass fraction of iron (Fe), magnesium (Mg) and silicon (Si), in mass fraction range more than 0.05 mg/kg in an alumina powder and similar matrices. All participants' DoE values were statistically indistinguishable from zero at 95 % confidence, demonstrating their competence within their respective levels of uncertainty. Therefore, CMCs that align with the "How Far the Light Shines" (HFTLS) statement can be supported by this CCQM-K144. To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).