Characterization and surface chemistry of uncoated and coated silicon nitride powders

Abstract

Various Si 3N 4 powders, produced by different procedures, were characterized by imaging (TEM) and analytical methods (EDS, FT-IR, XPS) in the as-received state as well as after doping with a metal oxide (MgO). For the doping, an alternative procedure to the usual methods, was applied, which is based on soluble organometallic compounds. Analytical transmission electron microscopy combined with lateral resolution element analysis and XPS measurements was used for morphological, structural and analytical characterization. The distribution of the dopant was deduced from measurements of XPS sputter depth profiles. These investigations were supplemented by FT-IR measurements in order to determine qualitatively and semi-quantitatively the reactive groups on the particle surfaces of the as-received powders. For comparison, measurements were performed with Si 3N 4 powders which were doped by the above chemical procedure and by mechanical mixing. The results of the various characterization methods are interpreted in the form of a model display for surface reactions of organometallic doping reagents on the surfaces of ceramic particles. The results show that Si 3N 4 powders with high concentration of OH groups on their particle surface reveal very good distribution of the fluxing element (layer-like coating).