An optical study of silicate glass containing Cr3+ and Cr6+

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