Infrared absorption in ThO2-doped Y2O3

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Abstract
The optical absorption has been measured over the 2–4‐μm region in dense polycrystalline Y2O3 containing 10 mole% ThO2 in solid solution. Measurements of the absorption coefficient (β) in ThO2‐doped Y2O3 indicated an intrinsic (multiphonon) level of 2.6×10−5 cm−1 at DF(3.8 μm) wavelengths although calorimetrically obtained β’s were in the low 10−3‐cm−1 region for the best materials. This difference is attributed to extrinsic absorption mechanisms and, in particular, to an impurity band of as yet undetermined origin lying directly between the DF and HF frequencies. Various ceramic processing techniques were applied to sintered ThO2‐doped Y2O3 ceramic to reduce this absorption with the most successful being a high‐temperature anneal in a higher partial pressure of oxygen.