MECHANICAL-PROPERTIES OF HOT-PRESSED TZP CERAMICS DOPED WITH Y2O3 ANDNB2O5

Y2O3 and Nb2O5 co-doped tetragonal ZrO2 polycrystals (TZPs) were synth esized by hot-pressing (HPing) at temperatures in the range of 1300 to 1500 degrees C to investigate the effect of alloying on the mechanica l properties of TZPs. TZPs (89.25 mol% ZrO2-5.75 mol% Y2O3-5.00 mol% N b2O5 and 90.24 mol% ZrO2-5.31 mol% Y2O3-4.45 mol% Nb2O5), prepared by HPing at 1400 degrees C for 1 h, showed a negligible monoclinic (m-) Z rO2 content (<1%), the highest flexural strength of about 1 GPa, and t he fracture toughness of above 7.5 MPa.m(1/2). Both low and high tempe rature (250 to 1000 degrees C) aging for up to 100 h was carried out t o evaluate the phase stability. TZPs, aged at temperatures higher than 400 degrees C, suffered from strength degradation due to the extensiv e cavitation caused by graphite oxidation. The carbon incorporated in TZPs was identified as either an ether-type C-O or a carbonyl-type C=O . On the other hand, the specimens aged at temperatures lower than 400 degrees C maintained the phase stability and mechanical properties.