Edward A. Maguire

Optical properties of ALON (aluminum oxynitride)

Aluminum oxynitride or ALON is a transparent polycrystalline ceramic material having high strength (380 MPa) and hardness (1950 kg/mm2). The transmission range of ALON extends from 0.2 micrometer in the UV through the visible to 6.0 micrometer in the infrared. This material is made by conventional powder processing and sintering a powder compact to full density and optical transparency. Powder compacts of near net shape and size are made by conventional dry pressing, by slip casting, and by injection molding methods. This gives the material great latitude in size and shape capabilities not afforded by materials formed by single crystal growth methods. Intrinsic transparency extending from ultraviolet wavelengths (UV) to mid-infrared wavelengths (MID-IR) and low levels of optical scatter have been achieved. In this paper recent measurements of the spectral dependence of forward optical scatter, the spectral emittance from room temperature to 1200 degrees Celsius, and the index of refraction (n) of ALON are presented. Literature values for the changes in refractive index with temperature (dn/dT) are compared.

Comparison Of Large ALON And Sapphire Windows

ALON (aluminum oxynitride) and sapphire windows measuring approximately 10 x 4 inches have been produced. Transmittance and mechanical durability in an extreme operational environment are essential for these windows. ALON is produced by ceramic powder processing techniques, while sapphire is grown as a single crystal. The ALON blank fabrication has been scaled up at Raytheon to produce several windows. Near net shape blanks were successfully polished to demanding optical and dimensional specifications at Zygo. Wavefront distortion and an atypical scattering phenomenon in large ALON windows are discussed. Sapphire windows were fabricated from plates cut from 10-inch diameter single crystal boules, using optical fabrication procedures similar to those developed for the ALON windows. The relative cost of optical fabrication of the two materials is discussed. Optical and mechanical properties for ALON and sapphire windows are presented.

Aluminum oxynitride's resistance to impact and erosion

Aluminum oxynitride (ALON) is a polycrystalline ceramic material useful for windows, domes, and other optical elements. It is transparent in the visible to mid-wavelength infrared. Data is presented on the affects of impacts with sand and water particles on polished surfaces. Velocities up to 690 m/sec were used.

Chemical Vapor Deposition Of Silicon Carbide For Large Area Mirrors

CVD-SiC has been identified as the leading mirror material for high energy synchrotron radiation because of its high K/a ratio and its ability to be super-polished to <10 A rms roughness. Technology already exists for depositing SiC over large areas (approximately 70 cm x 20 cm). The CVD process, substrate selection, and mirror design considerations are discussed.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.