THE EFFECT OF CERIA CO-DOPING ON CHEMICAL-STABILITY AND FRACTURE-TOUGHNESS OF Y-TZP

The fracture toughness and ageing resistance of yttria, ceria-stabiliz ed tetragonal zirconia polycrystals (Y, Ce-TZP) were evaluated as a fu nction of grain size and ceria content. Very fine grained, fully dense materials could be produced by sinter forging at relatively low tempe ratures (1150-1200 degrees C). The ageing resistance in hot water (185 degrees C) of 2 mol% Y2O3-stabilized TZP is strongly enhanced by allo ying with ceria. The ceria content necessary to avoid degradation comp letely, decreases with grain size. The toughness of fully dense Y, Ce- TZP is 7-9 MPa m(1/2) for grain sizes down to 0.2 mu m No or very litt le transformation took place during fracturing and no clear variation with grain size was observed for the toughness at grain sizes up to 0. 8 mu m. Reversible transformation and crack deflection may explain the observed toughness values.