article posted 22 March 2016
I am currently doing my PhD at the Otto-Schott-Institute of Materials Research in Jena, Germany. Among other things, I am dealing in my thesis with the structure of metaphosphate glasses. I received my diploma in chemistry from the same university in 2009. I spent almost two years at the j-fiber GmbH in Jena, working in the section for preform production.
Mixed cation effect in xMgO-(1-x)SrO-P2O5 metaphosphate glasses
K. Griebenow*1, D. Möncke1, U. Hoppe2, E.I. Kamitsos3, L. Wondraczek1
1Otto-Schott-Institute of Materials Research, Friedrich-Schiller University Jena, Fraunhoferstr. 6, 07743 Jena, Germany
2Institute of Physics, Rostock University, Albert-Einstein-Straße 24, 18059 Rostock, Germany
3Theoretical & Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece
In this work we investigate the mixed cation effect in Mg-Sr metaphosphate glasses xMgO-(1-x)SrO-P2
with 0=x=1. Nonlinear trends for mechanical and physical properties of glasses in this series were observed for glass transition temperature, molar volume, hardness and Young´s modulus, while a linear compositional dependence was found for Poisson´s ratio. The glass structure was investigated by vibrational (infrared, Raman) and NMR spectroscopy and by diffraction experiments. Figure 1 presents the correlation functions of characteristic glasses in the Mg-Sr series: The Mg-O peak at 0.21nm increases in intensity with increasing Mg content and the Sr-O peak at 0.26nm decreases in the same order.
Figure 1. Short-range distances in Mg-Sr metaphosphate glasses: experimental data (dots) and fits (lines).
Figure 2. Deconvolution of the normalized far-infrared spectra and compositional dependence of the cation-oxygen vibration in glasses xMgO-(1-x)SrO-P2O5.
Figure 2 presents deconvoluted far-infrared spectra of Mg-Sr metaphosphate glasses. The Sr-O vibration is located at 182 cm-1 in agreement with previous studies . Its intensity is decreasing with increasing Mg content, followed by two bands developing at 300 and 392 cm-1 where the Mg-O vibrations are expected. The varying intensities of the latter bands indicate a compositional dependence of the coordination sphere of Mg, resulting from a change in the coordination number and/or a change in the kind of phosphate species forming the coordination sphere.
 I. Konidakis, C.P.E. Varsamis, E.I. Kamitsos, D. Möncke, and D. Ehrt, J. Phys. Chem. C 114, 9125-9138 (2010); J. Phys. Chem. C 118, 25823-25823 (2014).