Ce-doped borosilicate (BSG), phosphosilicate (PSG), and borophosphosilicate (BPSG) glasses (B:P:Si molar ratios 8:0:92, 0:8:92, and 8:8:84; Ce:Si molar ratio 1 10-4 to 1 10-2) were prepared by the sol-gel method. High-resolution transmission electron microscopy (HRTEM), 31P, 29Si, and 11B magic angle spinning nuclear magnetic resonance (MAS NMR), electron paramagnetic resonance (EPR), and UV-vis absorption investigations demonstrated that, in PSG and BPSG, Ce3+ ions interact with phosphoryl, [OdPO3/2], metaphosphate, [OdPO2/ 2O]-, and pyrophosphate, [OdPO1/2O2]2-, groups, linked to a silica network. This inhibits both CeO2 segregation and oxidation of isolated Ce3+ ions to Ce4+, up to Ce:Si ) 5 10-3. In BSG, neither trigonal [BO3/2] nor tetrahedral [BO4/2]- boron units coordinate cerium; thus, Ce3+ oxidation occurs even at Ce:Si ) 1 10-4, as in pure silica glass (SG). The homogeneous rare-earth dispersion in the host matrix and the stabilization of the Ce3+ oxidation state enhanced the intensity of the photoluminescence emission in PSG and BPSG with respect to BSG and SG. The energy of the Ce3+ emission band in PSG and BPSG matrixes agrees with the phosphate environment of the rare earth.
Stability Of Luminescent Trivalent Cerium In Silica Host Glasses Modified By Boron And Phosphorus
CASU, MARIANO;MUSINU, ANNA MARIA GIOVANNA;
2005
Abstract
Ce-doped borosilicate (BSG), phosphosilicate (PSG), and borophosphosilicate (BPSG) glasses (B:P:Si molar ratios 8:0:92, 0:8:92, and 8:8:84; Ce:Si molar ratio 1 10-4 to 1 10-2) were prepared by the sol-gel method. High-resolution transmission electron microscopy (HRTEM), 31P, 29Si, and 11B magic angle spinning nuclear magnetic resonance (MAS NMR), electron paramagnetic resonance (EPR), and UV-vis absorption investigations demonstrated that, in PSG and BPSG, Ce3+ ions interact with phosphoryl, [OdPO3/2], metaphosphate, [OdPO2/ 2O]-, and pyrophosphate, [OdPO1/2O2]2-, groups, linked to a silica network. This inhibits both CeO2 segregation and oxidation of isolated Ce3+ ions to Ce4+, up to Ce:Si ) 5 10-3. In BSG, neither trigonal [BO3/2] nor tetrahedral [BO4/2]- boron units coordinate cerium; thus, Ce3+ oxidation occurs even at Ce:Si ) 1 10-4, as in pure silica glass (SG). The homogeneous rare-earth dispersion in the host matrix and the stabilization of the Ce3+ oxidation state enhanced the intensity of the photoluminescence emission in PSG and BPSG with respect to BSG and SG. The energy of the Ce3+ emission band in PSG and BPSG matrixes agrees with the phosphate environment of the rare earth.
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