In-situ Observation of Phase Separation During Growth of Cs2LiLaBr6:Ce Crystals Using Energy-Resolved Neutron Imaging

In-situ imaging and characterization of Cs2LiLaBr6:Ce crystal growth are performed utilizing energy resolved neutron imaging. The unique capability of neutrons to penetrate the furnace and to provide direct information on the materials within the furnace is used to visualize the growth dynamics, location, and shape of the liquid/solid interface and to map the elemental composition. Nontrivial dynamics of phase separation within the liquid and solid phases were observed and investigated. Quantitative projected two-dimensional maps of Li concentrations were obtained with sub millimeter spatial resolution delineating Li-rich and Li-depleted areas. Concurrent variations in Cs and Br concentrations were identified. Good transparency was obtained in part of the ingot where the liquid phase separation has reached steady state, suggesting that nonstoichiometric materials may be optimal for the original charge. The results demonstrate that energy-resolved neutron imaging and its associated modalities can provide unique information for the optimization of crystal growth conditions, in particular having the potential to accelerate scale-up from laboratory to commercial production by improving the yield and quality of single crystal materials.