Specifics of the growth of lithium-doped KCl single crystals by the Bridgman method in an argon atmosphere

Abstract A purification and growth process for alkali halide crystals (AHCs) is demonstrated using KCl: Li as a model system and employing an experimental crystal growth setup manufactured by Across International, USA. The process involves the following sequential stages: (i) deposition of a thin pyrolytic carbon coating (pyrolysis) onto the inner surface of a quartz ampoule in order to suppress the adhesion of molten alkali halide compounds (AHCs) to the ampoule walls; (ii) generation of a high vacuum (10 –6 Тоrr) inside the quartz reactor to purify the alkali halide raw materials from oxygen-containing impurities; (iii) establishment of an argon atmosphere (1.1–1.3 bar) and the quartz ampoule shielding as a technological approach for suppressing the evaporation of aggressive halogen vapors. Flame photometry, absorption spectroscopy, and luminescence spectroscopy analyses demonstrate that the KCl crystal matrix was purified from oxygen-containing impurities (OH) down to 0.2 ppm, divalent impurities (Me 2+ ) down to 0.1 − 0.3 ppm, and alkali-metal homolog cations (Li + , Na + ) down to 1–3 ppm. Unique capabilities of the facility were further realized in the growth of KCl single crystals doped with hygroscopic lithium ions. Enhanced scintillation and dosimetric properties of KCl: Li crystals were demonstrated.