Glass - Back to the Future!

Presenting Author:
Felix Lind

article posted 21 April 2016

Felix Lind graduated at the Friedrich Schiller University of Jena, Germany with a diploma in physics in 2014. Since 2015 he is PhD student at the Otto Schott Institute of Materials Research in Jena. The primary focus of his work is the investigation of induced structural changes in (boro-)silicate glasses and in glasses with highly polarizable cations.

Raman spectroscopic investigation of structural changes in ULE glass upon micro-indentation

F. Lind1*, R. Limbach1, D. Möncke1, E.I. Kamitsos2, S. Richter3,4, S. Nolte3,5, L. Wondraczek1

Ultra Low Expansion (ULE) glass, a binary TiO2-SiO2 glass with 7.5 wt% TiO2, was treated by micro-indentation and its structural variations were analysed by micro-Raman spectroscopy. The indent-induced structural changes and the response of glass against mechanical impact were found similar to other fully polymerized “anomalous” glasses such as vitreous SiO2 or Duran, all responding to indentation by densification. In particular, the Raman spectra of indented ULE glass show changes in the glass structure which can be correlated to anomalous densification-driven deformation mechanisms similar to vitreous silica and to commercially relevant specialty borosilicate glasses like the low-alkaline borosilicate glasses Duran and NBS2 [1]. Also, comparison is made here with data from the common soda lime silicate glass NCS, as this glass represents an example for “normal” shear-driven behaviour [2]. The glasses are further characterized by infrared spectroscopy, and for their mechanical properties by means of ultrasonic echography and nanoindentation. For verification of the results, the correlation to hydrostatic compression experiments (diamond anvil cell) is planned.

Typical changes in the Raman response of indented ULE glass are shown in Figure 1. They include the upshift of the 420 cm-1 band, which suggests changes of the Si-O-Si angle in silicate ring structures, as well as an increase of the intensity of the D1 band at 483 cm-1 (4-member rings) and the D2 band at 600 cm-1 (3-member rings). These silicate structural rearrangements from mostly 5- and 6-member rings to a higher fraction of 3- and 4-member rings lead to a decrease of the glass free volume. Very interestingly, this indentation-induced modification of the silicate structure is very similar to that found for laser-irradiated ULE glass [3]. Additionally, the 1100 cm-1 band, which was recently assigned to the symmetric stretching of Ti-O bonds in TiO4 tetrahedra [3], is found to decrease in relative intensity upon indentation of ULE (Fig. 1). The assignment of the 937 and 1110 cm-1 Raman bands to the asymmetric and symmetric stretching vibrations of TiO4 tetrahedra in ULE glass, respectively, was confirmed by combined polarized Raman and IR measurements [4].

Figure 1: Raman spectra of ULE glass before and after indentation.

[1] A. Winterstein-Beckmann, D. Möncke, D. Palles, E.I. Kamitsos, and L. Wondrazcek, J. Non-Cryst. Solids 401, 110 (2014).
[2] A. Winterstein-Beckmann, D. Möncke, D. Palles, E.I. Kamitsos, and L. Wondraczek, J. Non-Cryst. Solids 405, 196 (2014).
[3] S. Richter, D. Möncke, F. Zimmermann, E.I. Kamitsos, L. Wondraczek, A. Tünnermann, and S. Nolte, Opt. Mater. Express 5, 1834 (2015).
[4] I. Efthimiopoulos, S. Richter, D. Möncke, L. Wondraczek, S. Nolte, and E.I. Kamitsos, this Conference.

1Otto Schott Institute of Materials Research, Friedrich Schiller University, Jena, Germany
2Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens, Greece
3Institute of Applied Physics, Abbe School of Photonics, Friedrich Schiller University, Jena, Germany
4TRUMPF Lasertechnik GmbH, Ditzingen, Germany
5Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany