Several important physical properties of numerous samples of crystalline lithium fluoride have been measured; and wide variations were encountered, both among samples of air-grown and of vacuum-grown crystals, and between the two types. In general, the vacuum-grown crystals demonstrate the more desirable range of values, particularly with respect to good ultraviolet transmission, freedom from absorption at 2.8µ in the near infrared, high elastic limit, and small cold flow. However, the variation is so great that average. values cannot be relied upon in critical situations where large factors of safety cannot be invoked; in such cases, individual pieces must be measured for the properties of interest.
STANLEY S. BALLARD, LEWIS S. COMBES, and KATHRYN A. MCCARTHY, "Gross Variations in the Physical Properties of Synthetic Crystalline Lithium Fluoride," J. Opt. Soc. Am. 41, 772-775 (1951)