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The titanium coordination state and its temporal evolution in Li2O-Al2O3-SiO2 (LAS) glasses with ZrO2 and TiO2 as nucleation agents - A XANES investigation

 
: Kleebusch, E.; Patzig, C.; Krause, M.; Hu, Y.; Höche, T.; Rüssel, C.

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Ceramics international : CI 46 (2020), No.3, pp.3498-3501
ISSN: 0272-8842
English
Journal Article
Fraunhofer IMWS ()

Abstract
Lithium-alumosilicate glass-ceramics are widely used as zero thermal expansion materials. The effect of the nucleating agent can be monitored by the incorporation of titanium. In this study this has been done by X-ray absorption near edge structure, XANES, at the Ti–K-edge performed at a synchrotron. By contrast to a previous report which considered titanium as the only nucleation agent, the incorporation has been studied in two glasses doped with different Ti and Zr concentrations as nucleation agents which are close to compositions of industrial produced zero expansion materials. The glass samples were thermally treated at 740 or 750 °C for times of 0.25–24.00 h to achieve nucleation and crystallization. During the thermal treatment, different transformations on the nanoscale respective of the microstructure of the ceramic material take place. The coordination state of the titanium, which is included in all of the investigated compositions, enables a perception of the chemical backgrounds. The data set of the measured pre-peak of the Ti–K edge is a very sensitive indicator for the coordination state of Ti ions in glass of partially crystalline samples. The absolute energetic position and the normalized height vary systematically with the coordination numbers [4]Ti, [5]Ti or [6]Ti or actually mixtures thereof. The change in coordination state is visualized for all the compositions as a function of the crystallization time and correlated to the chemical composition of the samples.

: http://publica.fraunhofer.de/documents/N-582372.html