Flexible scintillation sensors for the detection of thermal neutrons based on siloxane 6LiF containing composites: Role of 6LiF crystals size and dispersion

he detection of thermal neutrons is increasingly important for several fields of interest, so new versatile, manageable and adaptable detectors are needed for applications in different environments and situations. To date, scintillators for thermal neutrons available on the market are fragile and with low adaptability. In this work, flexible and robust thermal neutron scintillators with improved properties as compared to commercial ZnS:Ag based phosphors are produced. The scintillators are produced by mixing ZnS:Ag powder and 6LiF nano-crystals in polysiloxane binders. 6LiF nano-crystals are synthesized by co-precipitation method, and the detection efficiency is optimized by tuning the crystal size through different solvent/co-solvent ratios. Then, the detection yield to thermal neutrons is investigated as related both to the crystal size and to the binder. Two different siloxanes, either with pendant phenyl groups or with aliphatic groups are used, the former being intrinsically fluorescent and with higher polarizability than the latter. The response to γ-rays is also evaluated. Lastly, the right combination of base resin and 6LiF crystals size allows to produce flexible scintillators for thermal neutrons with performances comparable to the commercial standard and with higher mechanical robustness and stability.