Laser-excited site-selective spectroscopy ofEu3+in sphene (CaTiSiO5) and glasses and glass ceramics of the sodium-calcium-aluminum titanosilicate system

Abstract

The ${}_{}{}^5{}_{}{}^{}\mathrm{D}_0^{}{}_{}{}^{}$→${\mathrm{}}^7$ ${\mathrm{F}}_0$,${}^7$ $F_1$ ,${\mathrm{}}^7$ $F_2$ emissions of europium(III) in a glass (sodium aluminosilicate), sphene ceramic [calcium titanosilicate (${\mathrm{CaTiSiO}}_5$)], and glass ceramic (microcrystalline sphene in a sodium aluminosilicate glass matrix) are reported. Fluorescence-line-narrowed emission excited by the ${}_{}{}^5{}_{}{}^{}\mathrm{D}_0^{}{}_{}{}^{}$←${\mathrm{}}^7$ ${\mathrm{F}}_0$ transition was used to sample the different coordination sites of ${\mathrm{Eu}}^{3+}$ represented by the inhomogeneously broadened absorption band. From the ratios of crystal-field parameters of the same order ($B_{22}$/$B_{20}$ and $B_{44}$/$B_{40}$) obtained from fitting the observed energy levels assuming $C_{2v}$ site symmetry, it was found that the sites ${\mathrm{Eu}}^{3+}$ occupies in the glass are adequately described by Brecher and Riseberg’s model of a ninth coordinating oxygen atom approaching a distorted Archimedian antiprism of oxygen atoms along the $C_2$ axis. At least two different coordination sites exist in the sphene ceramic, neither of which fits the above coordination scheme, but at least the geometrical coordination appears constant. Emission from ${\mathrm{Eu}}^{3+}$ in both the glass and sphene phases was observed from the glass-ceramic samples. Furthermore, a ${\mathrm{Eu}}^{3+}$ partitioning ratio of 8:1 (sphene phase to glass phase) is estimated from the ratios of integrated emission intensities.