Title
Effect of cooling on the optical properties and crystallization of UV-exposed photo-thermo-refractive glass
Abstract
Photo-thermo-refractive (PTR) glass is a multi-component silicate glass that undergoes a refractive index change after UV-exposure and thermal treatment. This photo-thermo-refractivity is due to the precipitation of sodium fluoride nano-crystals; thus the glass remains highly transparent in the visible and near-IR regions. Up to now, most studies focused on the influence of temperature and duration of thermal treatment on the PTR glass properties, but no attention was given to the cooling step after thermal treatment. In this paper, the influence of cooling on crystallization and resulting optical properties of UV-exposed PTR glass is studied. We show that cooling between the nucleation and growth treatments is a mandatory step to achieve the full benefits of the first heat-treatment, i.e., a large number of small crystals. We also show that the main part of the refractive index change occurs on the cooling path after pre-nucleation. Non-isothermal DSC study associated with in situ pre-nucleation treatment shows that pre-nucleation enhances crystallization only if the temperature is decreased below T(g) before the second (development) treatment. Using high temperature photometric measurements of the absorption spectra of UV-exposed PTR glasses, we tentatively associate that effect with the presence of liquid drops of a silver containing phase during regular pre-nucleation treatment. This fact explains the necessity to cool such drops below their melting point to obtain nucleation centers for efficient precipitation of NaF nano-crystals. (c) 2008 Elsevier B.V. All rights reserved.
Journal Title
Journal of Non-Crystalline Solids
Volume
354
Issue/Number
42-44
Publication Date
1-1-2008
Document Type
Article
First Page
4730
Last Page
4736
WOS Identifier
ISSN
0022-3093
Recommended Citation
"Effect of cooling on the optical properties and crystallization of UV-exposed photo-thermo-refractive glass" (2008). Faculty Bibliography 2000s. 656.
https://stars.library.ucf.edu/facultybib2000/656
Comments
Authors: contact us about adding a copy of your work at STARS@ucf.edu