Hochfeste Keramiken auf Al203- und Zr02-Basis durch kontrollierte Korngrenzenstrukturen.

Considering an increase in the fracture toughness, a smaller flaw size and reduced subcritical crack growth as three approaches to produce high strength ceramics, the paper emphasizes the influences of shaping technologies on the flaw size and of the grain boundary structure on subcritical effects. The micromechanical stability of grain boundaries is discussed in terms of the grain boundary fracture toughness, of the resistance against subcritical crack propagation, and of microflaws (the formation of which depends on residual microstresses and the local, microscopic viscosity on cooling the sintered bodies). Experimental evidence is presented for pure Al2O3 ceramics, for tetragonal ZrO2, and or TiC strengthened composites on the basis of Al2O3 and ZrO2, respectively