Method to assess the homogeneity of partially crystallized glasses: Application to a photo-thermo-refractive glass

Abstract

a b s t r a c tWe describe a new method for the study of both optical and crystallization homogeneity of partially crystallized glasses or glass-ceramics at different spatial scales (from 100 mm to 1 lm). The method relies on the association of different techniques, such as interferometry, optical microscopy and differential scanning calorimetry. The method was tested to probe the optical and crystallization homogeneity of both asmade and UV-exposed, and pre-nucleated samples of a photo-thermo-refractive (PTR) glass. This study demonstrates that pure UV-exposure did not lead to an improvement of the crystallization homogeneity of the glass. However, the benefit of associating UV-exposure and nucleation thermal treatment was clear. These combined treatments permit to homogenize the crystal distribution in PTR glass at millimeter and micron scale. This result is of major commercial interest.

Effect of cooling on the optical properties and crystallization of UV-exposed photo-thermo-refractive glass

“…This conclusion is supported by the fact that a large shift in the crystallization temperature was observed in quenched samples in Ref. [20].…”

“…It is seen that if temperature is decreased below 450°C, the crystallization temperature measured by DSC reaches a minimum of $600°C. If the temperature is not decreased after the pre-nucleation step, crystallization temperature lies within the same range of temperatures than that for PTR glass UV-exposed but not pre-nucleated [20]. Finally, if the temperature is decreased to between 450 and 500°C, the crystallization peak shifts to a temperature between 600 and 720°C.…”

Role of bromine on the thermal and optical properties of photo-thermo-refractive glass

“…This independence of T g on bromine concentration may be due to the fact that its concentration is very low and thus it does not change the glass viscosity significantly. Regarding crystallization, it was previously demonstrated [6] that PTR glasses pre-nucleated for 30 min at 510°C would exhibit a typical behavior, i.e. the crystallization peak of unexposed glass shifts down to 650°C, and the crystallization peak of UV-exposed glass shifts down to 600°C.…”

Nonlinear photosensitivity of photo-thermo-refractive glass by high intensity laser irradiation

“…Samples of PTR glasses of composition 15Na 2 O-5ZnO-4Al 2 O 3 -70SiO 2 -5NaF-1KBr-0.01Ag 2 O-0.01CeO 2 (mol%) were studied in this work as in previous works [6][7][8][9]. Technology of glass preparation is described in Ref.…”

“…Technology of glass preparation is described in Ref. [8]. Polished samples 25 Â 25 Â 2 mm 3 were prepared from each batch.…”