New Glass Family Demonstrates High Refractive Index, UV-Shielding Properties

A novel composition of germanosilicate glass, created by adding zinc oxide, has properties that could be valuable for lens applications. The new family of zinc germanosilicate glass was invented by a research group at The Pennsylvania State University (Penn State). Samples of the glass demonstrated a high refractive index, comparable to that of pure germania glass. The samples also showed high transparency, good UV-shielding properties, and good glass-forming ability, making them suitable for lens applications.

Ye Luo (right), doctoral student in materials science and engineering, pours the new composition of germanosilicate glass into form. Courtesy of Penn State.

By finding the optimum balance between zinc oxide and other components, the researchers were able to achieve a high refractive index in their glass while avoiding crystallization. “The motivation for the study was the need for new glass compositions that have a high refractive index while still being processable at an industrial scale,” said professor John Mauro. Researcher Ye Luo said that its high refractive index makes the new glass suitable for designing low-thickness lenses.

Zinc oxide showed UV-shielding properties in the study samples. With UV shielding, a zinc-oxide-containing glass could be used for everyday applications such as car windows and eyeglasses, said the team. The glass samples also showed favorable forming properties. As a “long glass,” the new compositions can be formed over a broader temperature range, making them simpler to manipulate during formation. This property — resistance to crystallization — and the lower cost of zinc oxide compared to germania could make the new glass composition a practical choice for manufacturing on a mass scale. The team has filed a patent for its zinc oxide-containing germanosilicate glass.

Germanosilicate glass is essential in the manufacture of optical amplifiers, waveguides, and solid-state lasers. The research was published in the Journal of Non-Crystalline Solids (https://doi.org/10.1016/j.jnoncrysol.2018.10.012).

Melting and pouring germanosilicate glass into form. Courtesy of Penn State EMS.