2006 Volume 114 Issue 1326 Pages 155-160
The doping dependence of high temperature plastic flow behavior in TiO2-doped, GeO2-doped and TiO2 and GeO2 co-doped tetragonal ZrO2 polycrystal (TZP) was systematically examined at 1400°C in air under an initial strain rate of 1.3×10-4 s-1. The amount of dopant cations was in the range of 0.2-4 mol%. The flow stress in the TZP decreases with the increasing doping amount in TiO2 and/or GeO2-doped TZP, but levels off over a 3 mol% addition in the GeO2-doped and TiO2-GeO2 co-doped TZP. The doping dependence of the flow stress in the TiO2-GeO2 co-doped TZP is close to that in the GeO2-doped TZP rather than to that in the TiO2-doped TZP; the flow stress in the GeO2-doped and TiO2-GeO2 co-doped TZP is significantly lower than that in the TiO2-doped TZP. The doped cations tend to segregate in the vicinity of the grain boundaries in TZP. The doping dependence of the flow stress is probably related to the amount of the grain boundary segregation of the dopant cations; the grain boundary segregation of the dopant cations is supposed to enhance the grain boundary atomic diffusion in the TZP, and hence the flow stress consequently decreases. On the other hand, elongation to failure in the TZP is highly improved by the TiO2 and/or GeO2 doping. The improved high temperature ductility of the TZP is attributed to the flow stress reduction due to the TiO2 and/or GeO2 doping.
