Viscous Slip along Grain Boundaries in Chlorine‐Doped Silicon Nitride

摘要: The effect of chlorine doping on the anelastic-relaxation and torsional-creep behavior a silicon nitride (Si{sub 3}N{sub 4}) polycrystalline body was studied. Two model polycrystals--one undoped other doped with small fracture chlorine--were investigated. Their microstructures consisted equiaxed well-faceted Si{sub 4} grains whose boundaries were separated by continuous, nanometer-sized film silica (SiO{sub 2}) glass. actual presence in polycrystal ascertained ion chromatography is thought to be enriched at grain boundaries. o intergranular structure characterized high-resolution electron microscopy. micromechanical response SiO{sub 2} boundary under shear stress monitored up very high temperatures (i.e., {approximately}2,000 C) internal-friction experiments. dopant, which network modifier glass that also causes widening grain-boundary film, significantly lowered bulk viscosity residual As consequence change chemistry, curve chlorine-doped material shifted toward lower rate markedly increased, as compared material. According viscoelastic themore » polycrystal, data resulted superposition two individual components: (i) relaxation peak related anelastic slip mechanism along (ii) background component results from an irreversible diffusional-creep mechanism.« less