Abstract
Sc2O3, HfO2 and Zr02 colloidal nanoparticles have been synthesised by sol-gel chemistry from organometallic precursor in alcoholic medium. Hafnia and zirconia particles were spherical and less than 5nm in diameter. Scandia particles were lozenge shaped platelets of 70 x 40 x 8nm in dimension. Sol stability was analysed by viscosity measurement. Particle morphologies were characterised by TEM, XRD and SAXS analyses. Scandia, hafnia and zirconia xerogels were obtained by solvent evaporation at room temperature and pressure. Bulk materials had structures, thermal stabilities and compositions deduced by XRD, TGA-DSC, EDX, N2-BET adsorption-desorption and FTIR spectrometry. Elementary analyses were undertaken to study the mechanisms of synthesis. Present and potential applications of the so formed xerogel materials are discussed. Optical coatings to be used at 351nm were produced on fused silica substrates by dip coating from stable scandia hafnia and zirconia sols. Coatings containing organic impurities were purified via chemical or thermal treatment, or solvent extraction. The optical properties (absorption, scattering, reflection, transmission, refractive index), compositions, homogeneity and surface topologies of these thin films were obtained by UV transmission, photothermal deflection at 520nm, XPS and AFM investigations. Resistance to laser radiation at 351nm was also measured for xerogel coatings of quarter wavelength thick. These coatings exhibited high refractive indices, good structural homogeneity and good resistance to laser damage. Future uses of such coatings are considered.