New Lanthanide-Containing Silicate Fluoride Scintillators for Radiation Detection

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Non-TechnicalBorder protection agencies, such as Homeland Security, must be able to detect rogue radiation sources, for example dirty bombs, before they are transported into the country. A pressing need exists for large quantities of materials know as scintillators, which are used in portable detection devices. Scintillators are materials that emit visible light when exposed to radiation, and the better the scintillator, the brighter the light and the smaller the amount of radioactive material that can be detected. This research, funded by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, involves the fundamental aspects of crystal growth of improved scintillating materials and thereby advances the field of radiation detection. In addition, this research project provides a valuable educational experience for graduate and undergraduate students. Conducting this research trains students in the art of crystal growth and teaches them the concept of experimental design and methods optimization. Overall, this research contributes to the education and training of a wide range of individuals, including those from underrepresented groups, in the area of solid state and materials chemistry.TechnicalOne area where the development of new functional materials can have a tremendous impact is homeland security. There exists a pressing need for large quantities of efficient scintillating materials for improved radiation detection. This research focuses on the synthesis of new neutron, X-ray, and gamma-ray activated scintillating oxides. Fluorine in mixed anion phases has been identified as one element that plays a crucial role in the intensity of fluorescence, and it has been demonstrated that fluorine can also increase the scintillation efficiency of rare earth silicates. Specifically, it is known that luminescent oxyfluorides in which the fluorine anions are located in LnOxFy polyhedra, such as in Cs3LnSi4O10F2 (Ln = Eu, Tb), a recently discovered brightly scintillating material, can exhibit scintillation as bright as Lu2SiO5:Ce3+. The targeted crystal growth of fluorine containing mixed-anion phases takes advantage of a recently developed enhanced flux growth technique that is known to yield crystals of oxyfluorides and salt-inclusion silicates. To better understand the processes involved in the formation of mixed anion phases in the various flux environments that are used for synthesis of complex oxide single crystals, in-situ neutron diffraction experiments are carried out to identify the optimal growth conditions for preparing new scintillators in the laboratory as well as to transform crystal growth from an empirical to a deliberate process. Additionally, this research contributes to the education and training of a wide range of individuals, including those from underrepresented groups, in the area of solid state and materials chemistry, for example through collaboration with Claflin University, an HBCU institution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.