Abstract
Since silicon nitride is fabricated using liquid phase sintering, sintering additives usually remain between Si3N4 grains as grain boundary phases. The grain boundary phases are softened and suddenly reduce the strength of sintered body under high temperature. This phenomenon occurs more notably when grain boundary phases contain glassy ones. The condition of grain boundary phases also influences the creep property under high temperature. This paper investigates the internal friction of Si3N4 sintered body, which relates to grain boundary slip and diffusion of atoms. This investigation will clarify the relationship between the conditions of grain boundary phases (ex. crystallization) and the internal friction changes. The creep properties of sintered body are also studied by analyzing the results of internal friction measurements. This will allow us to fully consider the relationship between the composition of sintering additives and the effects of heat treatment for crystallization.
