Internal Friction uder Low-Amplitude torsional and High-Amplitude Uniaxial Load in Silicon Nitride.

High temperatures stimulate thermally activated deformation mechanisms. For single crystal ceramics the consequences are limited up to temperatures of about 1400*C. However, for polycrystalline ceramic materials it has been observed that at temperatures typically in excess of 1000*C, the deformation behaviour becomes increasingly time-dependent. This phenomeno is known to be affected by grain boundary processes. In ceramics produced with liquid phase forming sintering additives the latter will remain at least partially in the grain boundaries after processing. Ceramics containing such amorphous intergranular phases (IGPs) are even more prone to changes of the mechanical behaviour at high temperatures, since at temperatures exceeding the glass transition temperature of the IGPs their viscosity drops.

DONZEL L.;  SARAGUCHI S.;  SCHALLER R.;  VAN DER BIEST Omer; 

1996-09-04

JRC13560