Sintering and hardness characterization of nanozirconia tapes

A stable tape casting suspension of a 3 mol% yttria stabilized tetragonal zirconia (3Y-TZP) powder of 27 nm particle size was developed with about 2.5 wt% of phosphate ester dispersant. Green nanozirconia tape cast by the conventional Doctor’s Blade technique was sintered to 65-80% relative density at 1200°-1400°C. The maximum tetragonal phase (98.16%) and densification (80%) were obtained at 1350°C. Vickers microhardness measured at 1.96-19.6 N loads showed an indentation size effect (ISE) for samples of various relative densities. At 19.6 N load, 80% dense tapes showed 12.51 GPa hardness. The highest value of Meyer’s constant (n) was 1.95. Per cent decrease in hardness with load was reduced with enhancement in relative density. As the load and hence the size of the indent is enhanced, the microplastic deformability may increase, thus leading to the observed indentation size effect