Laser spectroscopy and electron paramagnetic resonance of Cr3+ doped silicate glasses

Gels and glasses in the SiO2-Al2O3-ZnO-Cr2O3 and SiO2-Al2O3-MgO-Cr2O3 syste ms were synthesized by the solgel method. A description of the change of th e Cr3+ environment during the xerogel-glass-glass ceramic transformation is presented using optical properties of Cr3+ ions. Absorption and emission s pectra, electron paramagnetic resonance measurements, and site-selective la ser spectroscopy were performed to characterize the Cr3+ fluorescent center s. Absorption and fluorescence are interpreted by structural considerations showing the variation of Cr3+ environment during heat treatment. By heatin g glasses, the glass-ceramics containing chromium-doped ZnAl2O4 (gahnite) a re formed. The results indicate the presence of chromium ions in a gahnite crystalline phase and emission from the E-2 level is observed. Also a Cr3fluorescence centered at 770 nm results from T-4(2) level of Cr3+ sites at low ligand field in glassy phase. (C) 2000 Elsevier Science B.V. All rights reserved.