Direct analysis of Al2O3 powders by total reflection X-ray fluorescence spectrometry
A direct analysis procedure for the determination of trace impurities of Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Ga in Al2O3 ceramic powders by total reflection X-ray fluorescence spectrometry (TXRF) is described. The powders were analysed in the form of slurries containing 1–10 mg mL−1 of powder. The use of the procedure in the case of powders with differing grain size and for different slurry concentrations was investigated. Three different quantification possibilities were compared, namely the use of Al as a matrix component, the use of Fe as a trace element contained in the sample or of Co added in concentrations of 200 μg g−1 as internal standard. The homogeneity of elemental distributions in sample layers deposited on the TXRF quartz carriers by evaporating 5 μL of the 10 mg mL−1 slurries was studied by scanning the 4- to 5-mm-diameter spots of two samples by synchrotron radiation TXRF at Hasylab. For powders with differing graininess but mainly finer than about a few 10 μm, no systematic influence of the grain size on the accuracy of the determinations of Ca, V, Fe, Ni, Cu and Zn could be observed. The measurement precision, however, seemed to be limited by inhomogeneous distributions of the trace elements in the samples as testified by the synchrotron radiation TXRF scans. Detection limits of the developed TXRF procedure for Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Ga were found to be in the 0.3–7 μg g−1 range and were shown to increase slightly with the grain size of the samples. Quantification using Al (matrix) as internal standard led to systematically higher values out of the accuracy required, whereas the other two approaches in all cases led to reliable results.
Slurry Sampling Electrothermal Atomic Absorption Spectrometry for the Analysis of Aluminum-Based Ceramic Powders
A slurry sampling electrothermal atomic absorption spectrometry method for the determination of Ca, Cr, Cu, K, Fe, Mg, Mn, Na, Ni, and Zn in aluminum oxide and aluminum nitride powders is described. For each analyte, the experimental conditions including atomization temperature, internal gas flow during atomization, and pyrolytic re-coating of the graphite tube were optimized with respect to the sensitivity and background absorption. Quantification was performed by means of calibration curves recorded with the use of aqueous standards. The achievable limits of detection are between 5 ng/g (K) and 130 ng/g (Fe). The accuracy was checked by comparison of the results with those obtained by instrumental and radiochemical neutron activation analysis and other methods.
Secondary ion mass spectrometric determination of impurities in aluminium oxide
Impurities in aluminium oxide (alumina) were determined by secondary ion mass spectrometry (SIMS), which enabled the sample powder to be analysed without time-consuming pre-treatment stages. The difficulty of acquisition of standard samples associated with quantitative SIMS was overcome by preparing chemically the standard samples in powder form and applying the calibration graph method. The four elements (Ca, Fe, Ga and Ti) in an alumina reference material and commercial alumina samples were determined successfully and the results agreed well with those of inductively coupled plasma atomic emission spectrometry. The procedures are described and experimental results presented.