High-performance spinel ceramics for IR windows and domes

摘要

High performance spinel ceramic is required for near-term future applications based on the excellent spinel transmission properties in the UV-VIS-Mid IR wavelength range. Windows as large as 30"x60" and hemispherical domes 4"-7" in diameter have been distinguished as applications where the novel spinel technology could be successfully applied. Future applications involve the use of even more complex 3-D shapes like spinel superdomes and tubes. The thickness of some of these components has reached 1" and above. MER has been actively pursuing these design objectives and has shown the feasibility of producing some of these complex shaped parts. Optimization of transmittance and strength are always the main objective. MER has also been pursuing edge bonding technology, where large thick panes will be edge bonded into a final large window. The production of monolithic windows as large as 18"x22", which can be used as individual windows or as panes prior to edge bonding, has also been demonstrated. Using the complex 3-D spinel process, MER has also demonstrated the feasibility of producing 4"-7" diameter hemispherical domes blanks of very high quality. After rendering and polishing, defect free domes have been produced. The process has been characterized and qualified using an optical grade spinel specification. Details of MER's technology to produce low cost, high strength, transparent magnesium aluminum spinel windows and domes are described. High optical and IR transparency in the 0.3 - 5.5 μm wavelength range is obtained. Equibiaxial strength averages 180-200 MPa, with individual readings reaching 300-320 MPa maximum. Spinel optical and mechanical properties are provided.