Depth profiling of oxygen in oxidized ceramic Si3N4 with the backscattering technique

The internal oxidation of reaction sintered Si3N4 during creep measurements at high temperatures has been measured with the MeV 4He backscattering technique. A computer program has been used to generate theoretical spectra which are fitted to the experimental spectra and thus determine the composition. The measurements reveal that the bulk material is contaminated with calcium and iron which diffuse to the surface during the heat treatment. At the surface the material is completely oxidized to SiO2 and an appreciable amount of oxygen has been diffused throughout the whole material. (Auth.)