article posted 28 Jun 2016
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
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
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
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.