George C. Wei

Enhancement in aerothermal shock survivability of lanthana-strengthened yttria windows and domes

Experiments aimed at improving the physical properties of transparent polycrystalline lanthanastrengthened yttria (LSY) infrared windows and domes were conducted. The objective was to enhance the thermal shock resistance for aggressive aerothermal environments. The approach included improving the average equibiaxial flexure strength, Weibull modulus, and other relevant physical properties. Initial results of an extensive study on polishing and post-fabrication treatment along with improved powder processing showed an -30% strength improvement without sacrifice in optical properties, leading to an appreciable increase in the calculated survivability. LSY with a low lanthana content significantly enhanced predicted survivability.

Scattering in lanthana-strengthened-yttria infrared transmitting material

Lanthana-strengthened yttria (LSY) is a window and dome material for 3 - 5 micrometers IR applications. Scattering, an important optical property of LSY, was measured using a scatterometer method and integrating sphere technique. The scatterometer results were correlated with the integrating sphere results. The mechanisms of forward scattering in LSY are discussed.