January 2000 Ž . Materials Letters 42 2000 200–206 www.elsevier.comrlocatermatlet Preparation and characterization of Al and B co-doped cerium containing sol–gel derived silica glasses A. Patra ) , G. De, D. Kundu, D. Ganguli Sol–Gel DiÕision, Central Glass and Ceramic Research Institute, JadaÕpur, Calcutta 700 032, India Received 12 April 1999; accepted 1 August 1999 Abstract Glasses containing Ce were prepared by the sol–gel method at 10008C. Two parallel series of experiments, one in oxygen and other in nitrogen atmosphere, were carried out for synthesis, where parallel series of glasses were prepared with addition of boron and aluminium. The densification behaviour of the gels has been studied by physical property measurements, as also UV–Visible–NIR and FTIR spectroscopy. The shifting of the absorption cut-off of the glasses towards shorter wavelengths with change in the atmosphere from oxygen to nitrogen and also with addition of boron or aluminium co-doping indicate that the concentration of Ce 4q ions is decreased. This is proposed to take place through electron trapping 4q Ž 3q . by Ce leading to formation of Ce and hole trapping by non-bridging oxygens. q 2000 Elsevier Science B.V. All rights reserved. PACS: 82.70.Gg; 81.20.Pe; 76.30.Kg; 33.20.Lg; 33.20.Kf; 33.20.Ea Keywords: Sol–gel; Glasses; Cerium; UV–Visible–NIR spectroscopy 1. Introduction Glasses doped with different rare-earth ions are wx potential candidates for optical applications 1. wx Cerium-doped glasses have many applications 1; among those, one of the most important applications of these glasses is as cover glasses on solar cells in wx space satellites 2 . Such glasses should have good radiation stability, UV light cut-off and high visible Ž transmission properties. These glasses 100-mm . Ž. thick should have 1% transmission T between 300 and 320 nm, 50% T at 345 nm and above 86% T in wx the visible range 2 . Cerium ions have two types of ) Corresponding author. Ž . E-mail address: apatra@cscgcri.ren.nic.in A. Patra 3q Ž . 4q Ž . oxidation states, i.e., Ce cerous and Ce ceric in oxide glasses. The proportion between the two oxidation states depends on both the basicity of the wx glass matrix and the preparation conditions 3 . The Ž . effect of co-dopants e.g., Al and P was found to influence the oxidation states and fluorescence prop- wx erties 4 . The co-doping effect can be explained by changes in the coordination structures including co- ordination number, symmetry and basicity of oxygen ligand. Only a limited amount of work has been per- formed on the behaviour of cerium-doped silica w x glasses prepared by sol–gel processing 5–8 . In the present work, an investigation was made on sol– gel-derived Al and B co-doped cerium containing silica glasses for evaluation of the effect of the 00167-577Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0167-577X 99 00184-6