~tv ~1 1-wen/e, Fucullv of Cl'~errHc~Jl 'Techn~d~gv. l.aN~ral~rv I'~r [m~rgunic C'hem~strv, Mutermls Scwnce und Culal~'w~, P(). B~x 21'7. 7'~()()AE. E.nschede. 'The Nelherland,, (Ret'el~,ed ,2 t ,lime I~-) L) ;,, uccepled I '~ (.)ch~ber Iq~4 t) ,4 b,.~l l'u~'! ,]u amlll'slS tS prt'seulud o/ gralu ,t~lO111/i tllld th'll,~l~COtl/m o/ rttrla-crllo ,~_taluh:t'd tetlagOlla/ .llT'Ollltl Imlrcrrstal,~ ' (]',('e 'I'ZPs) u,~'lllg both i,~'/~thrrllla[ alld IlOll-I,~'otllerllla/ Icl']llllqllr,~ T/lu ch/Ir tl¢'lt'rlSlll'S O/)', Ct' 'I~ZP.~ ' or'(' i'olup, lred 11/ thosr o/)'.

The effects of compressive deformation on the grain boundary characteristics of fine-grained Y-TZP have been investigated using surface spectroscopy, impedance analysis, and transmission electron microscopy. After sintering at low temperature (11SO"C), the grain boundaries are covered by an ultrathin (1 nm) yttrium-rich amorphous film. After deformation at 1200"-1300°C under low stress, some grain boundaries are no longer covered by the amorphous film. Yttrium segregation seems to occur only at wetted grain boundaries. Evidence has been found that the extent of dewetting increases with increasing applied stress.

No abstract

The fracture toughness and ageing resistance of yttria, ceria-stabilized tetragonal zirconia polycrystals (Y, Ce-TZP) were evaluated as a function of grain size and ceria content. Very fine grained, fully dense materials could be produced by sinter forging at relatively low temperatures (11 50-1200 ~ The ageing resistance in hot water (185 ~ of 2 mol % Y203 -stabilized TZP is strongly enhanced by alloying with ceria. The ceria content necessary to avoid degradation completely, 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 ~tm. No or very little transformation took place during fracturing and no clear variation with grain size was observed for the toughness at grain sizes up to 0.8 pm. Reversible transformation and crack deflection may explain the observed toughness values.