Mechanical Properties of Silicon Nitride Ceramics Containing Yb2O3 Sintering Additives

We have studied the effect of Yb2O3 additions on the phase composition and mechanical properties of Si3N4 ceramics and shown that, in all of the samples studied, the Yb4Si2O7N2 compound was a major component of the grain boundary phase, with ytterbium silicates as minor phases, whose content has been found to increase with increasing Yb2O3 concentration in the starting powder mixture. The bending strength of the ceramics has a tendency to decrease with increasing sintering additive content at both room temperature and 1600°C. The load–displacement curves obtained at 1600°C point to plastic deformation and creep of the material, the latter increasing with increasing Yb2O3 content, which is due to incomplete crystallization of the grain boundary phase.