title: Stability of luminescent trivalent cerium in silica host glasses modified by boron and phosphorus.
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 x 10(-)(4) to 1 x 10(-)(2)) were prepared by the sol-gel method. High-resolution transmission electron microscopy (HRTEM), (31)P, (29)Si, and (11)B magic angle spinning nuclear magnetic resonance (MAS NMR), electron paramagnetic resonance (EPR), and UV-vis absorption investigations demonstrated that, in PSG and BPSG, Ce(3+) ions interact with phosphoryl, [O=PO(3/2)], metaphosphate, [O=PO(2/ 2)O](-), and pyrophosphate, [O=PO(1/2)O(2)](2)(-), groups, linked to a silica network. This inhibits both CeO(2) segregation and oxidation of isolated Ce(3+) ions to Ce(4+), up to Ce:Si = 5 x 10(-)(3). In BSG, neither trigonal [BO(3/2)] nor tetrahedral [BO(4/2)](-) boron units coordinate cerium; thus, Ce(3+) oxidation occurs even at Ce:Si = 1 x 10(-)(4), as in pure silica glass (SG). The homogeneous rare-earth dispersion in the host matrix and the stabilization of the Ce(3+) oxidation state enhanced the intensity of the photoluminescence emission in PSG and BPSG with respect to BSG and SG. The energy of the Ce(3+) emission band in PSG and BPSG matrixes agrees with the phosphate environment of the rare earth.
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, INSTM, via Cozzi 53, 20125 Milano, Italy.
authors.forename: Carmen
authors.initials: C
authors.lastname: Canevali
authors.forename: Mariachiara
authors.initials: M
authors.lastname: Mattoni
authors.forename: Franca
authors.initials: F
authors.lastname: Morazzoni
authors.forename: Roberto
authors.initials: R
authors.lastname: Scotti
authors.forename: Mariano
authors.initials: M
authors.lastname: Casu
authors.forename: Anna
authors.initials: A
authors.lastname: Musinu
authors.forename: Radenka
authors.initials: R
authors.lastname: Krsmanovic
authors.forename: Stefano
authors.initials: S
authors.lastname: Polizzi
authors.forename: Adolfo
authors.initials: A
authors.lastname: Speghini
authors.forename: Marco
authors.initials: M
authors.lastname: Bettinelli
mesh_terms: D000042:Absorption; D001895:Boron / Q000737:chemistry*; D002563:Cerium / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005898:Glass / Q000737:chemistry*; D049408:Luminescent Agents / Q000737:chemistry*; D008163:Luminescent Measurements; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D010758:Phosphorus / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D049408:Luminescent Agents; D010758:Phosphorus; D002563:Cerium; D012822:Silicon Dioxide; D001895:Boron