Extremely suppressed grain growth of Y₂O₃ -stabilized zirconia nanocrystals synthesized by the nonhydrolytic sol-gel technique

Yttria-stabilized zirconia (YSZ) nanocrystals (NCs) have been synthesized by a nonhydrolytic sol-gel technique using the alkylhalide elimination reaction between the zirconium and yttrium isopropoxides and zirconium chloride in the oleylamine at 340°C. The grain growth behavior during heating of the agglomerated NCs up to 1000°C of the resulting NCs was studied underO ₂ atmosphere. Colloidal solutions of well-crystallized YSZ NCs, whose average size was approximately 3 nm, were successfully obtained for various yttria concentration, x in (Zr1-x Yx) O2-δ, of 0<x<0.34. For the (Zr0.85 Y0.15) O2-δ NCs, no distinct grain growth was observed below 700°C, and their average grain size was suppressed to 5-8 nm even when heating at 800°C. As compared with the YSZ NCs synthesized by the aqueous solution technique, whose grains grew to at least 15 nm in size when heated at 800°C, the present nonhydrolytic sol-gel technique resulted in NCs possessing an extremely suppressed grain growth characteristic. The suppressed grain growth was related to the hydroxyl defect-free nature and high crystallinity of the YSZ NCs synthesized by the nonhydrolytic sol-gel technique, in contrast to the aqueous solution technique, which results in amorphous complex oxyhydroxides.