article posted 14 April 2916
 D. Möncke, G. Tricot, D. Ehrt, E. I. Kamitsos, Connectivity of Borate and Silicate Groups in a Low-Alkali Borosilicate Glass by Vibrational and 2D NMR Spectroscopy, Journal of Chemical Technology and Metallurgy, 50 (2015) 381-386.
 D. Möncke, G. Tricot, A. Winterstein-Beckmann, L. Wondraczek, E.I. Kamitsos, On the Connectivity of Borate Tetrahedra in Borate and Borosilicate Glasses, Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B, 56 (2015) 203-211.
 D. Möncke, D. Ehrt, E.I. Kamitsos, Spectroscopic study of manganese-containing borate and borosilicate glasses: cluster formation and phase separation, Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B, 54 (2013) 42-51.
 D. Möncke, E.I. Kamitsos, A. Herrmann, D. Ehrt, M. Friedrich, Bonding and ion–ion interactions of Mn2+ ions in fluoride-phosphate and boro-silicate glasses probed by EPR and fluorescence spectroscopy, J. Non-Cryst. Solids, 357 (2011) 2542-2551.
From preferential bonding via clustering to phase-separated borosilicate glasses – a multi spectroscopic approach
Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Germany
In low alkali borosilicate glasses, all states from preferential bonding to clustering and to visible phase separation with physical interfaces are known to occur.
While the addition of small amounts (~1mol%) of Al2
can prevent phase separation, vibrational and 2D NMR spectroscopy show a preference for B-O-B and Si-O-Si bonds over
bonds when the samples are properly annealed. More interestingly, while rapidly quenched samples show both B4
-O-Si and B3
-O-Si bonds (with B4
denoting four- and three-fold coordinated boron, respectively), the number of mixed bonds decreases significantly in annealed samples and, of the remaining mixed bonds,
-O-Si links are strongly favoured over B4
-O-Si bonds [1, 2].
Addition of small amount (0.05 to 4 mol%) MnO to a duran glass, converts neutral BØ3
into charged metaborate [BØ]4
- tetrahedra (Ø denotes bridging oxygen ions).
tetrahedra bond preferentially to the borate rather than to the silicate network,
ions cluster near [BØ]4-
tetrahedra, a transition from preferential
bonding to finally visible phase separation is observed . The increased clustering of Mn2+
ions can be followed by electron spin resonance and photo-luminescence spectroscopy, and the change in the network structure by infrared spectroscopy.
Interesting is the strong exchange narrowing of the ESR signal, which indicates strong Mn-Mn interactions, as found in edge sharing clusters of Mn2+
New data from Raman measurements coupled to a DSC will be provided from which new insights into the temperature dependent preferential bonding and the transition from nano- to micro-scale phase-separation will be deduced.