Effect of powder dispersion on sintering behavior and mechanical properties of nanostructured 3YSZ ceramics

The aim of this work was to investigate the feasibility of producing dense nanostructured ceramics from commercial zirconia nanopowder by colloidal processing. Our study has demonstrated the adverse effect of the presence of aggregates in the production of nanostructured components. Two techniques were employed to remove aggregates – centrifugation and high energy milling. The finer powder thus produced by centrifugation and/or high energy milling, with an average size of particles around 60–70 nm was consolidated into a green body by a relatively simple low pressure filtration technique (300 kPa). It was possible to prepare green bodies of 47% density with relatively fine and uniform size pores from suspensions containing these powders. The green compacts obtained from finer powder could be sintered to fully dense nanostructured products at a significantly lower temperature (1200 °C) with a soaking period of 0.5 h only with an average grain size of 90 nm only in the sintered compact. In contrast the as received aggregated powder could not be sintered at all to full density even at as high temperature as 1600 °C. The bulk nanostructured 3 mol% yttria stabilized zirconia (3YSZ) compact with an average grain size of 110 nm exhibited Vickers hardness of 12.8 GPa, which is comparable to the available results in the literature.