Matrix–filler interactions in polysilazane-derived ceramics with Al2O3 and ZrO2 fillers

Interactions between a poly(vinyl)silazane and Al2O3 or Y2O3-stabilised ZrO2 fillers were studied during the fabrication of polysilazane-derived bulk ceramics in order to investigate the influence of oxide fillers on the resulting properties. Specimens were produced by coating the filler powders with the polysilazane, warm-pressing the resulting composite powders, and pyrolytic conversion in flowing N2 at various temperatures between 1000 and 1400 C. Significant differences in densification were seen, depending on the filler used. Reactions between the polysilazane-derived matrix and Al2O3 or ZrO2 at temperatures of 1300 C and above resulted in the formation of Si5AlON7 or ZrSiO4, respectively. Reactivity in the polysilazane-derived component was a result of SiO2 contamination caused primarily by adsorbed species on the filler particle surface. Knowledge of polysilazane/filler interface processes is important in helping predict properties such as shrinkage and porosity, which heavily influence the performance of a material.