Ceramic Composites of 3Y-TZP Doped With CuO: Processing, microstructure and tribology

In recent years, 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) doped with copper oxide has obtained increasing interest due to its enhanced superplasticity and good potential in tribological applications. In this work, the effect of addition of small amounts (0.8 mol%) of CuO on the sintering behaviour of 3Y-TZP was studied using a dilatometer and high temperature X-ray diffraction. A qualitative sintering model was established based on several reactions during sintering as indicated by thermal analysis and XRD. Some of these reactions remarkably retard densification and consequently result in low final density (86%) of the sample sintered at 1400 oC in air. The reaction between molten Cu2O and yttria as segregated to the Y-TZP grain boundaries is recognised to result in a significant destabilisation of the tetragonal zirconia phase. A relatively higher oxygen partial pressure can inhibit the dissociation of CuO to Cu2O. This inhibition in dissociation is one of the reasons why a dense (> 96%) 0.8 mol% CuO doped 3Y-TZP ceramic can be obtained after sintering at 1400 oC in flowing oxygen.