Structural characterization of some sol–gel derived phosphosilicate glasses L. Todan a , E.M. Anghel a,⇑ , P. Osiceanu a , R.V.F. Turcu b , I. Atkinson a , S. Simon b , M. Zaharescu a a Romanian Academy, Institute of Physical Chemistry ‘‘Ilie Murgulescu’’, Spl. Independentei 202, 060021 Bucharest, Romania b Babes-Bolyai University, Faculty of Physics & Interdisciplinary Research Institute on Bio-Nano-Sciences, 400084 Cluj-Napoca, Romania highlights  Triethyl-phosphite/phosphate (TEP) and H 3 PO 4 were P-sources to obtain 10P 2 O 5 –90SiO 2 .  Spectral data by NMR, Raman, XPS and XRF was obtained for these gels and glasses.  Un-hydrolyzed TEP in gel underwent partial vaporization and degradation by annealing.  A 1.84 higher P 2 O 5 /SiO 2 ratio was found for the H 3 PO 4 derived glass than TEP one. graphical abstract article info Article history: Received 16 September 2014 Received in revised form 3 December 2014 Accepted 6 January 2015 Available online 23 January 2015 Keywords: Phosphate glasses Sol–gel method Nuclear Magnetic Resonance (NMR) Raman spectroscopy Photoelectrospectroscopy (XPS) X-ray fluorescence (XRF) abstract A comparative study of three phosphosilicate gels of the 90SiO 2 –10P 2 O 5 composition obtained from tetraethoxysilane and three phosphorous precursors: triethylphosphate (TEP), triethylphosphite (TEPI) and H 3 PO 4 is performed. 29 Si and 31 P Magic Angle Spining NMR, X-ray Photoelectron, X-ray Fluorescence and Raman spectroscopies as well as TG analysis are used in order to establish phosphorous precursors and annealing influence on composition and structure of the outcome materials. Unlike the three dimen- sional silicate network made of Si(OSi) x (OH) 4x species, unreacted TEP (100% Q 1 condensed phosphorous units) from TEP derived gel and a large amount of isolated phosphorous species (39.7% Q 0 ) in the H 3 PO 4 derived gel are identified. Annealing at 700 °C of the three gels give similar structure with the 90SiO 2 – 10P 2 O 5 glass, excepting the triethylphosphate derived glass that has a much lower P content. Thus, the H 3 PO 4 derived glass at 700 and 1000 °C shows 1.89 and 1.94 times higher P 2 O 5 /SiO 2 ratios than in the case of the TEP derived one. Ó 2015 Elsevier B.V. All rights reserved. Introduction Phosphate glass-containing materials have numerous technological uses (rare-earth ion hosts for solid-state lasers, pla- nar waveguides, biomaterials, proton-conducting glass-based com- posite membranes for fuel cell, low-temperature sealing glasses etc.) due to their low melting temperature, high dimensional stability, ionic exchange and electrical conductivities [1–3]. Although, phosphosilicate glasses can be obtained by classical methods, their sol–gel synthesis offers the advantages of a lower cost process and advanced mixing of the starting materials up to molecular scale [4]. Various phosphorous precursors were employed along with tetraethoxysilane (TEOS) for sol–gel synthesis of the phosphosilicate gels. The mostly used phosphorous precursors in the sol–gel method were H 3 PO 4 , OP(OC 2 H 5 ) 3 (TEP) and http://dx.doi.org/10.1016/j.molstruc.2015.01.012 0022-2860/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +40 21 316 79; fax: +40 21 312 11 47. E-mail address: eanghel@hotmail.com (E.M. Anghel). Journal of Molecular Structure 1086 (2015) 161–171 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc