AN OPTICAL STUDY OF SILICATE GLASS CONTAINING CR3+ AND CR6+ IONS

The optical properties of chromium-doped sodium silicate glass synthes ized under oxidizing conditions have been investigated. The method of preparation provides a large concentration of Cr6+ ions, but absorptio n and emission spectra showed that a small amount of Cr3+ (and Cr5+) i ons are always present. The Dq-, B- and C-parameters of the crystal-fi eld theory for the Cr3+ ion were obtained, confirming the glassy natur e of the sample. Cr3+ luminescence was observed in the near-infrared r egion, even at room temperature, confirming the low value of the cryst al-field Dq. Moreover, the high ultraviolet transparency of this matri x allows observation of a well resolved absorption spectrum of the Cr6 + ion.