Cr3+ and Cr4+ luminescence in glass ceramic silica

This paper reports on the effect of glass ceramic silica matrix on [CrO4]4- and Cr2O3 NIR and visible luminescence. Chromium-containing silica was obtained by precipitation from water-glass and chromium nitrate acid solution with thermal treatment at 1000 deg. C. From XRD results silica and silica-chromium samples are crystalline. The chromium emission spectrum presents two main broad bands: one in the NIR region (1.1-1.7μm) and other in the visible region (0.6-0.7μm) assigned to Cr4+ and to Cr3+, respectively. This thermal treated glass ceramic silica-chromium sample stabilizes the [CrO4]4- where Cr4+ substitutes for Si4+ and also hexacoordinated Cr3+ group probably as segregated phase in the system. It can be pointed out that luminescence spectroscopy is a powerful tool for detecting the two chromium optical centers in the glass ceramic silica