Growth and Hardening of Alkali Halides for Use in Infrared Laser Windows
Annual technical rept.
OKLAHOMA STATE UNIV STILLWATER DEPT OF PHYSICS
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Several undoped and Sr doped KCl crystals were grown from reagent grade powder in a crystal puller recently placed in operation. The Sr concentration in the doped crystals was varied from a few up to 650 parts per million ppm molar. The engineering flow stresses or yield points of these reagent grade crystals were measured. Values obtained range from 300 psi for undoped crystals to 2550 psi for the most heavily doped crystal. These results, as well as the Vickers microhardness results, are in good agreement with measurements on crystals grown at Oak Ridge National Laboratory ORNL using purified powders. The flow stress of high purity KCl from ORNL is found to increase from an unirradiated value of 300 psi to 2700 psi at an electron radiation dose which has introduced a Clo interstitial concentration of 65 ppm. The increase in flow stress is directly proportional to the square root of the defect concentration for both Sr doped and irradiated KCl crystals. This result is in good agreement with Fleischers theory.