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°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°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°C) aging for up to 100 h was carried out to evaluate the phase stability. TZPs, aged at temperatures higher than 400°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°C maintained the phase stability and mechanical properties.