DEVELOPMENTS IN HIGHLY TOUGHENED CEO2-Y2O3-ZRO2 CERAMIC SYSTEM

A wet-chemical approach has been applied to derive fine powders with various ceria and yttria compositions in the CeO2-Y2O3-ZrO2 ceramic system by the co-precipitation method. The characteristics of the as-derived powders have been evaluated through differential thermal analysis, thermogravimetric analysis, BET surface-area analysis, and inductively coupled plasma technique. The hardness and fracture toughness of the as-sintered specimens were evaluated by the indentation method. A highly toughened ceramic with K(IC)>25 MPa m1/2 was achieved with the composition 5.5 mol % CeO2-2 mol % YO1.5-ZrO2. The relationship between the mechanical properties and the compositions of stabilizers, CeO2 and Y2O3 is discussed with respect to the degree of tetragonal to monoclinic transformation as well as the grain size of the as-sintered ceramics.