Additive coloring rate and intensity for pure and doped fluorite crystals

The mechanism of the additive coloring of calcium fluoride crystals, both pure and doped with I- and III-group elements, has been investigated. The coloring rate and intensity and the dependences of these parameters on the experimental conditions, vapor mixture pressure, and temperature have been experimentally determined. It is shown that the concentration of anion vacancies/electrons that can be introduced into crystals is in the range of 10(17)-10(18) cm(-3); in crystals with a high concentration of rare earth ions, the limiting concentration can be an order of magnitude higher.