Glass - Back to the Future!

Presenting Author:
Nadja Lönnroth

article posted 28 Jun 2016

Nadja Lönnroth

Dr. Nadja Lönnroth is a Senior Research Scientist in the glass research group at Corning Incorporated. Nadja earned her MSc in physics from Helsinki University in 1999 and her PhD from Aalborg University in 2007 on the topic of physical properties of basaltic glasses. She joined Corning Incorporated in 2011 and has worked with a wide variety of glasses from borates and phosphates to silicates investigating their structure-property relationships.

Precipitation of copper halides in aluminoborosilicate glasses

Nadja Lönnroth*, Nicholas Borrelli and Roger Araujo
Science and Technology, Corning Incorporated, Corning, NY

Precipitation of copper halide crystals in glass demonstrates two interesting optical phenomena. First is that copper halide nanocrystalline phase produces a distinct room temperature excitonic absorption feature that can be tuned from near UV to visible wavelengths by varying the Cl/Br ratio. The second is that copper halide phase has been shown to exhibit photochromic behavior. Past studies have shown that the maximum precipitation of copper halide is observed when R=(R2O-Al2O3)/B2O3 is in the range of 0.15-0.45, where a boron coordination change upon heat treating the glass drives the precipitation of Cu-halide.

In this work we study the precipitation of copper halide crystals in sodium alkali aluminoborosilicate glasses at a constant silica level. We observe Cu-halide precipitation in the regime with excess alkali and high boron content, not directly connected to the R-value. This is also the region where the melted glasses are more oxidized and have higher halide losses. An effort is made to explain what changes occur when composition changes are made in the Na2O-Al2O3-B2O3 composition space; how the glass structure is tied to halide retention, oxidation state variations and finally the precipitation of the Cu-halide phase and the onset of photochromism.