Thickness alteration of grain-boundary amorphous films during creep of a multiphase silicon nitride ceramic

Experimental observations of the creep response of a commercial sintered si licon nitride ceramic are presented. The stable microstructure of this mate rial at high temperature contains secondary crystalline phases which result from partial devitrification of the intergranular phase, The widths of amo rphous films along grain boundaries (between silicon nitride grains) and ph ase boundaries (between silicon nitride and secondary phase grains) are cha racterized by transmission electron microscopy, The thickness distributions of grain-boundary films before and after creep are analyzed by a statistic al method, While the film widths are highly uniform before creep, a bimodal distribution is observed after creep. The results suggest that viscous flo w of the boundary amorphous films occurs during creep deformation.