Fluorine-containing lanthanum borate glasses colored by oxides of the d- and f- elements

Glasses of the superheavy crown glasses have a high refractive index, which gives the possibility of fabricating from them pieces simulating precious stones. Colored glasses of this type have not been previously studied. The present work investigates colored glasses produced on the base of a glass belonging to the superheavy crown type, the foundation for which was the system Zn0.sCd0.sB204-YF~. Introduction of YF 3 into the composition had a favorable effect on their technological arzd optical properties. Different coloring components and their combinations were studied. The glasses were founded in a laboratory electric furnace using vitreous carbon crucibles at a temperature of II00*C, with isolation of the melt from air atmosphere. Thus, a characteristic of the founding conditions was a reducing atmosphere over the melt. Special purity and analytical grade reagents were used for charge preparation. The absorption spectr a of the glasses were made in the region 250-900 nm using a "Specord" M40 spectrophotometer. The coloring agent content in the glasses and their principal spectral characteristics are shown in'Table I. The position and relative intensity of the absorption bands in glasses 1-4 dependent on presence of rare-earth ions (Pr 3+ and Nd 3+) agree well with the data obtained for glasses with other matrix compositions [I, 2]. The insignificant effect of composition and also the founding conditions on the color of glasses containing individual rare-earths is explained by a shielding of the f-electrons responsible for the appearance of a color, from excitations arising during change of the external surrounding [2]. In the spectra of glasses 2-4, containing jointly PrzO 3 and NdzO3, the Pr 3+ and Nd 3+ bands remain unchanged, i.e., these ions occur in the role of individual coloring agents, which agrees with the data obtained for silicate glasses [3]. In the spectra of glasses 5-9, containing CoO and NizO3, the absorption bands are situated in the same region as in silicate glasses colored by (Co2+)~ and Cr 3+, having an octahedral coordination [4]. The spectrum of glass I0, containing Cr203, exhibits bands corresponding to Cr 3+, in which the position is somewhat shifted relative to the bands in silicate glasses in the short wavelength region. Such a shift is characteristic of boroncontaining glasses [5]. Glass ii, containing VzO~, exhibits bands in the region characteristic of V 5+ in silicate glasses [4]. During joint presence of CrzO 3 and VzO s (glass 12), the spectrum exhibits the absorption band of Cr 3+. A small amount of V 3+ ions is suggested, whose bands are situated in the same spectral region as the Cr 3+ bands. However, the vanadium is apparently mainly present in the V s+ form, which does not color the glass, while the chromium exhibits the Cr 3+ form. In the spectra of glasses 13 and 14, the Cr z+ and (CoZ+)6 ions appear probably as individual coloring centers, since the absorption intensifies in the region around 600 nm, where their bands exist jointly. In the spectra of glasses containing Sbz05, which was introduced to induce the most complete possible transfer of cobalt (glass 15) and chromium (glass 16) to the (CoZ+)8 and Cr z+ states, only the absorption bands of the mentioned ions are present. The spectra of glasses 17-21 did not exhibit absorption bands in the spectral region studied. In the spectrum of the manganese-containing glass 22, bands are observed in the region characteristic of Mn 2+ ions in silicate glasses [4]. With joint presence in the glasses of the oxides of bin, Nd, and Ce (compositions 23 and 24), the spectra exhibit bands of Mn z+ and Nd 3+ ions, each of which appears as an individual coloring agent. The bands of