Single Crystal Growth of LiF with OH- and Mg2+ Activators and Evaluation of Optical Characteristics of Color Centers Induced by Ionizing γ- Radiation

Crystal of LiF were grown by a home-made Czochralski system using MgF2 (0.05%), LiOH (0.1%) and Li2CO3 (0.05%) powders as the impurities after purification by the zone-melting method. Another crystal was  also grown with raw materials with the normal purity of 99.995%. The grown crystals were found to be colorless and transparent with no cracks. In order to obtain a high concentration of F2+ centers and small concentration of colloids and parasitic aggregate centers, the grown crystals were subjected to the multi-step ionizing irradiation treatments. At the same time, maintaining the highest possible density of F2+-like centers and small cluster centers caused  the effective thermal stability of F2+- centers and in particular reduced the formation of the electron color centers which improved the stability of the optical features of the modified LiF:F2+** crystals. As a result, acting as a color center laser medium. A comparing of the features of crystals shows that their optical characteristics are the same as the other samples. The XRD properties of the grown crystals were also investigated for the comparison. They indicated the Faced-Centered Cubic (FCC) structures of the crystals. In addition, the inductively coupled plasma (ICP) analysis was used to measure the Mg2+ ion concentration. The emergence of OH- peaks was specified by a FTIR spectrophotometer. In a long run, the spectroscopic characteristics of the new F2+- centers in LiF:OH, Mg crystals were also studied.