Fabrication of polycrystalline IR-transparent ceramics: A potential substitute for Sapphire

"Sapphire has been the dominant infrared transparent material for quite some time, and polycrystalline materials such as, magnesium fluoride, aluminum oxynitride and yttrium oxide, have been used to a limited extent when the performance criteria have beenless stringent. Polycrystalline and transparent oxide ceramics that have a cubic crystal structure offer an opportunity as a replacement for sapphire, provided a fine grain size is maintained in the fully sintered state. Starting from high qualitynanopowders and using a relatively new near net shape consolidation technique, we have sintered a variety of oxide ceramics to full density with a fine grain size. Building upon this work, in Phase I of the program, we propose to fabricate a fully sinteredand transparent oxide ceramic, and characterize the mechanical and optical properties. Prototype windows and domes will be fabricated in Phase II and provided for field testing. Working with our collaborators in the industry and a federal laboratory, bothof whom have offered support for the proposed program, we anticipate transitioning the technology into military and commercial applications by the end of Phase II. Transparent ceramics offer a number of different opportunities in both military and civilianapplications, including infrared windows in heat seeking missiles and optical systems. A powder consolidation approach, which is the subject of this proposal, is an attractive low cost alte