C 3412 (OTTO) Cadmium telluride pieces, 1-12 mm, 99.9999% Cas 1306-25-8 - used as an infrared optical material for optical windows and lenses and is proven to provide a good performance across a wide range of temperatures. An early form of CdTe for IR use was marketed under the trademarked name of Irtran-6 but this is obsolete.