AFRL Increases Production Size of Sapphire Sheets for Windows Published Jan. 12, 2012 By Heyward Burnette, AFRL/RXOB Materials and Manufacturing WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- Air Force Research Laboratory Materials researchers teamed with Saint-Gobain Ceramics and Plastics Inc., to develop new manufacturing processes that increase the size and thickness of sapphire sheets for electro-optic (EO) and infrared (IR) windows. This collaborative work pushed the state of the art in large-aperture windows to accommodate sizes 16 inches wide by 18 inches long and 0.8 inches thick. The new repeatable process for growing large, thick sapphire windows meets all transmission and durability requirements. The repeatable process also offers a reduction in post-production costs. The demand for large-area windows for EO and IR applications in the visible to mid-wave infrared spectrum has increased considerably in the last 10 years. Applications in both the military and civilian arenas, such as for aircraft, missiles and ships, require hard, strong and transparent materials in order to achieve system goals. Sapphire possesses the desired properties for windows that are required to operate in a harsh EO or IR environment. However, there are only a limited number of crystal growth techniques able to produce single crystal sapphire suitable for window applications larger than 6 inches, and only a few of them are capable of producing commercially available plates in larger sizes that are suitable for fabrication into a finished window. AFRL and Saint Gobain Ceramics and Plastics Inc. extended the state of the art of EFG for growing near net shape sapphire. They conducted design experiments, thermal modeling and experimental growth trials; the new size capability serves as an enabler for the sapphire sheets required by the Navy's DDG 1000 (Zumwatt-class destroyer) program. The manufacturing process is also under evaluation by the Air Force's Cobra Ball aircraft and by the Army's High Mobility Artillery Rocket System Office.