Secondary ion mass spectrometry analysis of iron oxides with known ¹⁸O/¹⁶O contents

Abstract

Iron oxide films with known "0 and l60 content were prepared by thermal oxidation of iron metal in H,180/H,160 gas mixtures at 400°C. The oxide films were analysed in four laboratories with SIMS within a month after they were produced. One oxide sample (with 91% "0) was also analysed after storage in air for 15 months. It turns out that the oxides are stable over that time period. The yield ratios of the detected ionic species based on negative '*O and I6O ions and metahxygen-containing ions were compared with the nominal, known values. The effect of interference of residual l6O and 160H on the results is discussed and appropriate measures for reducing this effect are proposed. Reasonably good agreement is found between the four laboratories.