Research may lead to better UV/radiation blocking in eyeglasses

Posted Dec 16, 2009 by Bob Ewing
Penn State researchers have found adding cerium oxide to phosphate glass rather than the commonly used silicate glass may make eyeglasses able to block ultraviolet light.
The glasses will also have an increased radiation damage resistance while remaining colorless.
It is possible there are a number of commercial applications for these new eyeglasses.
In the Penn State press release, Jen Rygel, graduate student in materials science and engineering said, "We wanted to get larger amounts of cerium into glass, because of its beneficial properties, and then investigate the properties of the glasses,"
Rygel, and Carlo Pantano, distinguished professor of materials science and engineering and director of Penn State's Materials Research Institute synthesized and compared 11 glasses with varying concentrations of cerium, aluminum, phosphorus and silica.
There worked showed that it was possible to make phosphate glasses with 16 times more cerium oxide than silicate glasses while maintaining the same coloration and ability to absorb ultraviolet light. The research was published in the Dec. 15 issue of Non-Crystalline Solids.
"We were able to get a lot more cerium into our phosphate glass without sacrificing the optical transmission -- they both still looked clear," added Rygel.
The two cerium states -- cerium (III) and cerium (IV) -- are shifted to absorb less blue light in phosphate glasses and this may be way the researchers succeeded.
"A good example is in solar cells," said Rygel.
"The wavelengths that solar cells use aren't ultraviolet, and actually ultraviolet radiation can cause damage to the electronics of a solar cell. If you add cerium to the glass you can prevent the ultraviolet from getting down to the photovoltaic cells, potentially increasing their lifetime."
Cerium additions do more than block ultraviolet light by increasing a glass's cerium concentration it is possible to increase its resistance to radiation damage from x-rays and gamma rays by capturing freed electrons.
"Radiation can kick electrons free from atoms," said Rygel. "You can see this by looking at what happens to a Coke bottle over time. It darkens because of radiation exposure."
The National Science Foundation and the U.S. Air Force Research Laboratory supported this work.