Size Effects on the Stabilization of Ultrafine Zirconia Nanoparticles

The spontaneous oxidation of crystallized ZrAu at room temperature leads to the formation of ultrafine monoclinic zirconia (MZ) particles (about 3.6 nm in diameter). The presence of tetragonal phase (TZ), generally observed in very small zirconia particles, was investigated by X-ray diffraction and Raman experiments but was not observed. Thermodynamical calculations considering the finite size effects in zirconia were introduced to explain the formation of pure MZ considering experimental and theoretical surface energies. The results of these calculations associated with the near equilibrium conditions used for synthesis demonstrate that the monoclinic structure is the stable crystallographic structure of zirconia nanocrystals at room temperature.