Stability of Luminescent Trivalent Cerium in Silica Host Glasses Modified by Boron and Phosphorus

• Published in: Journal of the American Chemical Society 2005-10, Vol.127 (42), p.14681-14691
• Main Authors: Canevali, Carmen, Mattoni, Mariachiara, Morazzoni, Franca, Scotti, Roberto, Casu, Mariano, Musinu, Anna, Krsmanovic, Radenka, Polizzi, Stefano, Speghini, Adolfo, Bettinelli, Marco
• Format: Article
• Language: English
• Subjects: Absorption; Boron - chemistry; Cerium - chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron Spin Resonance Spectroscopy; Exact sciences and technology; Glass - chemistry; Luminescent Agents - chemistry; Luminescent Measurements; Magnetic Resonance Spectroscopy; Microscopy, Electron, Transmission; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other solid inorganic materials; Particle Size; Phosphorus - chemistry; Photoluminescence; Physics; Silicon Dioxide - chemistry; Surface Properties
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja052502o

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, [OPO3/2], metaphosphate, [OPO2/ 2O]-, and pyrophosphate, [OPO1/2O2]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.