Abstract
Sol-gel technique utilizing hydroxypropyl cellulose (HPC) polymer as a steric stabilizer, has been used to synthesize nanocrystalline zirconia (ZrO2) powder. Various analytical techniques such as transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), x-ray photoelectron microscopy (XPS) and x-ray diffraction (XRD) are used to characterize the as-synthesized and calcined nanocrystalline ZrO2 powder. The high temperature metastable tetragonal phase stabilization in undoped nanocrystalline ZrO2 particles is studied in view of three different phase stabilization mechanisms. It is revealed that these phase stabilization mechanisms operate depending on the average ZrO2 nanoparticle size within the as-synthesized nano-sized ZrO2 powder, which in turn can be effectively controlled by adjusting the sol-gel processing parameters involving the ratio of molar concentrations of water and zirconium (IV) n-propoxide (R), the concentration [HPC] and the molecular weight (MWHPC) of the HPC polymer. The variation in the relative volume fraction of tetragonal phase (VT) as a function of R and [HPC] is explained on the basis of variation in the average ZrO2 nanoparticle size and the operation of dominant metastable tetragonal phase stabilization mechanism as a function of R and [HPC].