ABSTRACTThe inert gas condensation (IGC) technique was employed to synthesize non-agglomerated nanoparticles of ZrO2 and Y2O3 with different average particle sizes ranging from 4 to 14 run. The sintering behaviors (in air and vacuum) of single phase n-ZrO2 (monoclinic crystal structure) and Y2O3-ZrO2 mixture (Y-TZP) were studied in terms of densification rate and final sintering temperature. There was a strong correlation between densification characteristics and properties of the starting powder compacts such as average particle size, particle and pore size distributions. n-ZrO2 was sintered to full density in air at temperatures as low as 1125°C (0.47 Tm) and in vacuum at 975 °C (0.42 Tm). Although the grain sizes in the fully sintered samples were well below 100 nm, the grains had grown by a factor of 10 as compared to the initial particle size. Therefore, a pressureassisted sintering technique was employed to further reduce the densification temperature and final grain size. Threshold effects in this process are also discussed.