Analysis of impurities in high-purity aluminum oxide by glow discharge mass spectrometry

A method has been developed for determining trace components in high-purity aluminum oxide powder for making sapphire single crystals. The analyses have been performed with VG9000 glow-discharge mass spectrometer which provided a sensitivity at the sub-ppm level. To analyze nonconducting specimens, a secondary cathode made of high-purity Ta foil was employed. Effects have been determined from factors that influence the sensitivity. Mathematical simulation has been used in calculating the effects of molecular ions on the results. Isotopes are identified that provide the necessary analysis sensitivity and accuracy. The method allows one to distinguish impurities adsorbed on the particles from those that enter into the crystal lattice.