Various semiconductors were evaluated for use as infrared optical materials. The materials evaluated include gallium arsenide, gallium phosphide, germanium, silicon, zinc sulfide and diamond. The method used to produce the materials is reviewed. Semi-insulating polycrystalline gallium arsenide was produced by a horizontal Bridgman process to sizes of 8 by 12 by 0.7 inches. Gallium phosphide was produced by a liquid encapsulated Czochralski technique to 2-inch diameter and 3-inch length. Germanium was obtained commercially from a casting technique. High-resistivity silicon having a 1-inch diameter and 6-inch length was obtained from a float-zone process. Zinc sulfide was obtained commercially from a chemical vapor deposition process. Polycrystalline diamond was obtained by a microwave chemical vapor deposition process. The optical, electrical, mechanical, and thermal properties of these materials are presented and compared. Thermal shock, rain erosion, and modulation transfer function analyses were performed, and the results for each material are presented and compared. It was found that all these materials have useful physical properties as infrared optical components in a wide range of applications.