Mechanical properties of ATZ-type composites obtained in the sintering process of zirconia powders with different chemical composition

Composites based on tetragonal zirconia, containing corundum inclusions (alumina toughened zirconia, ATZ), are one of the basic and more commonly used ceramic structural materials. The mechanical properties of this type of composites, mainly strength and fracture toughness, strongly depend on their chemical and phase composition as well as their microstructure. The purpose of this work was to obtain ATZ composites in the sintering process of two ZrO2 powders with different chemical composition with a small (1.5 wt%) addition of nanometric corundum powder, as well as to determine their microstructure and basic mechanical properties. Nanometric powders of pure zirconia and zirconia containing 4 mol% yttrium oxide were used, and their amounts in the mixture with nanocorundum were selected so that the final product had a nominal 3 mol% Y2O3. To this powder mixture, 10% or 20% by volume of submicron corundum powder was added, after which the compacts were sintered at 1450 °C for 2 h. The material obtained in this way was characterized by a higher value of the critical stress intensity factor, but a lower bending strength in relation to the sintered body obtained under the same conditions from a single-phase powder. The presence of alumina grains in each case increased both fracture toughness and strength.