Effect of Y2O3 addition on the phase transition and growth of YSZ nanocrystallites prepared by a sol-gel process

The effect of Y2O3 addition on the phase transition and growth of yttria-stabilized zirconia (YSZ) nanocrystallites prepared by a sol-gel process with various mixtures of ZrOCl2 · 8H2O and Y(NO3)3 · 6H2O ethanol-water solutions at low temperatures has been studied. DTA/TGA, XRD, SEM, TEM and ED have been utilized to characterize the YSZ nanocrystallites. The crystallization temperature of 3YSZ, in which Y2O3/(Y2O3 + ZrO2) = 0.03, gel powders estimated by DTA/TG is about 427 °C. When 3YSZ and 5YSZ gels are calcined at 500-700 °C, their crystal structures as composed of coexisting tetragonal and monoclinic ZrO2, and tetragonal phase decreases with calcination temperature increasing from 500 to 700 °C. Pure cubic ZrO2 is obtained when added Y2O3 is greater than 8 mol%. A nanocrystallite size distribution between 10 and 20 nm is obtained in TEM observations.