ULTRAFINE-GRAINED DENSE MONOCLINIC AND TETRAGONAL ZIRCONIA

Nanoparticles of ZrO2 with diameters ranging from 4 to 8 nm were synthesized by gas condensation. As-prepared n-ZrO2 particles have a monoclinic and a high-pressure tetragonal structure depending on size. Pure ZrO2 was sintered to full density under vacuum at 0.4T(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 ZrO2 stabilized with 3 mol% Y2O3 was prepared by interdiffusion of nanoparticles and sintered to near-theoretical density.