Ultrafine‐Grained Dense Monoclinic and Tetragonal Zirconia

Nanoparticles of ZrO 2 with diameters ranging from 4 to 8 nm were synthesized by gas condensation. As‐prepared n ‐ZrO 2 particles have a monoclinic and a high‐pressure tetragonal structure depending on size. Pure ZrO 2 was sintered to full density under vacuum at 04 T m within the monoclinic phase field. Final grain sizes in theoretically dense pellets are below 60 nm. By sintering below the monoclinic–tetragonal transition temperature, microcracking was completely avoided. Tetragonal ZrO 2 stabilized with 3 mol% Y 2 O 3 was prepared by interdiffusion of nanoparticles and sintered to near‐theoretical density.