X‐ray induced AES study of the effect of chemically bound hydrogen on the oxidation kinetics of an Si 3 N 4 powder

Silicon nitride powders manufactured by the pyrolysis of silane and ammonia were found to contain chemically bound hydrogen. Most of this hydrogen could be removed by vacuum annealing at 1000°C. In the present study, x‐ray‐induced AES has been used to determine the oxidation kinetics for vacuum‐annealed Si 3 N 4 powders that were heated in air at temperatures between 850 and 975°C. The average oxide thickness on the surface of the powder particles for each temperature and oxidation time was calculated from the ratio of the SiO 2 to Si 3 N 4 Si KLL peak intensities. The results are compared with those for the as‐manufactured powder, which contained the hydrogen impurity. For both annealed and unannealed powder, the oxidation rate was linear within the temperature range 850–1000°C. Within this temperature range, the oxidation rate was significantly higher for the vacuum‐annealed Si 3 N 4 powder.