Papers by Author: M. Elisa

Abstract: The investigated ecological glasses with no toxic compounds, such as BaO, PbO, As2O3, As2O5, fluorine, CdS and CdSe in their composition are located in ternary and quaternary oxide systems: ZnO-SiO2-TiO2 and SiO2-R'2O-R''O-R'''O2, where R' is Na or K, R'' is Ca or Mg and R''' is Zr or Ti. The first system contains P2O5, ZnO and TiO2 in order to obtain opal glasses, without fluorine compounds. The second system replaces the barium oxide and lead oxide with potassium, magnesium, zirconium and titanium oxides, for materials like lead free crystals. The raw materials can be replaced by silicate or borosilicate glass waste. The advantages of borosilicate glass waste are: bringing valuable components into recipes (B2O3, CaO, Al2O3), saving raw materials and energy, creating an ecological environment The characteristic temperatures (vitreous transition point, low and high annealing points, softening point) and the thermal expansion coefficient of the glass are presented. The FTIR and Raman spectroscopy provided structural data, such as characteristic vibration maxima for silicon and titanium oxide, and revealed the role of zinc oxide in the vitreous network. The refraction index and UV-VIS transmission are discussed.

Abstract: A wet non-conventional method for preparing aluminophosphate glasses is presented. Aluminophosphate glasses belonging to the oxide system Li2O-BaO-Al2O3-La2O3-P2O5, doped with rare-earth ions (Pr3+, Er3+, Gd3+, and Yb3+) were obtained. The influence of the doping ions on the optical properties of the phosphate glasses has been investigated in relation with micro-structural and local electronic phenomena The optical behavior of Li2O-BaO-Al2O3-La2O3-P2O5 glasses doped with 3% mol. rare-earth ions has been studied by ultra-violet-visible-near-infra-red (UV-VISNIR) spectroscopy. The transmission spectra revealed electronic transitions between 4f and 6s inner orbital of the rare-earth ions. Structural information via optical phonons was provided by infra-red (IR) absorption spectra in the range 400-4000 cm-1. IR optical phonons are characteristic for the vitreous phosphate network, showing out the glass network-forming role of P2O5. The absorption spectra present the main PO2 and P-O-P symmetrical stretch modes besides P-O-P bend mode, P-OH, P=O, PO3 2-, asymmetrical and symmetrical vibration modes. Fluorescence spectra of the rareearth- doped aluminophosphate glasses, in the visible range, were obtained by laser excitation at 514.5 nm. The fluorescence signals revealed specific electronic transitions, which provide visible and near-infra-red emission. Glasses containing rare-earth ions exhibit luminescence at the following wavelengths: Pr3+ ions at 820 nm and 880 nm, Er3+ ions at 520 nm, 550 nm and 560 nm, Gd3+ ions at 530 nm, 540 nm, 550 nm 820 and 880 nm, Yb3+ions at 530 nm, 540 nm, 550 nm and 980 nm.