Effect of Nb2O5 and Y2O3 alloying on the mechanical properties of TZP ceramics

In the ZrO2-Y2O3-Nb2O5 ternary system, Nb2O5 and Y2O3 co-doped tetragonal ZrO2 polycrystals (TZPs) were synthesised by sintering and hot-pressing (HPing) to evaluate the effect of alloying on the mechanical properties and phase stability of TZPs. Monolith containing the composition of 90.24 mol% ZrO2-5.31 mol% Y2O3-4.75 mol% Nb2O5, which was prepared by both sintering and hot-pressing, exhibited a good relation between strength and toughness. Also, no t-->m phase transformation after ageing at temperatures in the range of 100 to 400 degrees C for up to 1000 h was observed. TZPs sintered at 1550 degrees C for 10 h in air showed the flexural strength of above 500 MPa and the fracture toughness of 9 MPa m(1/2). The flexural strength increased greatly by HPing at 1400 degrees C for 1 h under an Ar gas atmosphere from 500 MPa to above 1 GPa, while the fracture toughness decreased slightly from 9 MPa m(1/2) to 7.5 MPa m(1/2). (C) 1998 Elsevier Science Limited and Techna S.r.l. All rights reserved.