Mechanical properties of hot-pressed TZP ceramics doped with Y2O3 and Nb2O5

Abstract

Y2O3 and Nb2O5 co-doped tetragonal ZrO2 polycrystals (TZPs) were synthesized by hot-pressing (HPing) at temperatures in the range of 1300 to 1500 degrees C to investigate the effect of alloying on the mechanical properties of TZPs. TZPs (89.25 mol% ZrO2-5.75 mol% Y2O3-5.00 mol% Nb2O5 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-) ZrO2 content (<1%), the highest flexural strength of about 1 GPa, and the fracture toughness of above 7.5 MPa.m(1/2). Both low and high temperature (250 to 1000 degrees C) aging for up to 100 h was carried out to evaluate the phase stability. TZPs, aged at temperatures higher than 400 degrees C, suffered from strength degradation due to the extensive 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.