Ytterbia-neodymia-costabilized TZP-Breaking the limits of strength toughness correlations for zirconia?

TZT ceramics were manufactured by hot pressing of pyrogenic zirconia nanopowder which was costabilized by 1 mol% ytterbia and 2 mol% neodymia (1Yb-2Nd-TZP) via the nitrate route. The evolution of microstructure, phase composition and mechanical properties with variation of sintering temperature from 1200 degrees C to 1400 degrees C was investigated. 1Yb-2Nd-TZP consists of a bimodal microstructure of small very transformable tetragonal grains and large cubic grains. At intermediate sintering temperature the materials combine a bending strength of 1250 MPa with a fracture resistance >13 MPa root m. The high threshold stress intensity of 7 MPa root m indicates high resistance to subcritical crack growth. An increase in fracture resistance before the crack tip induced by compressive residual stress shifts the strength toughness correlations to higher values than previously considered possible. (C) 2012 Elsevier Ltd. All rights reserved.