Influence of a grain-locking morphology on properties of doped ZrO2 ceramics made with ultrafine (∼3 nm) nanoparticles

The use of ultrafine (similar to 3 nm) nanoparticles of 10 mol.% CaO-doped ZrO2 together with a minimum dwelling time (15 min.) during pressureless sintering yielded high (> 99%)-density ceramic with a unique grain-locking microstructure; no impurity or second phase segregation was observed in the 'locked' regions. Although the normal X-ray diffraction data indicated a phase-pure cubic symmetry for the ceramic, Rietveld analysis confirmed a cubic-phase majority (similar to 83%) with minor tetragonal content (similar to 17%). The microstructure (homogeneously present on both top and interior of ceramics) for the sintered ceramics contributed in achieving high hardness (similar to 14 GPa); obtained hardness and indentation toughness values were also comparable to the previously reported cubic ZrO2 ceramics (doped with Y2O3). Considering the high cost of yttria-doped zirconia systems, the suitability with mechanical properties together with high sintered density for the present system suggests its potential usability at larger scales as an alternative to Y2O3-stabilized zirconia ceramics.