Investigation of the Microstructure and Scintillation Properties of Ce-Doped CaF2/LiF Eutectics for Thermal Neutron Detection

With the growing global emphasis on nuclear reactor decommissioning, reliable thermal neutron detection has become increasingly important for ensuring critical safety and for the identification of fuel debris and radioactive waste. In this context, this study developed and characterized a Ce-doped CaF₂/⁶LiF (Ce:CaF₂/LiF) eutectic scintillator for thermal neutron detection with Ce concentrations ranging from 0.5 to 10 mol%. The eutectic samples were grown by the melt-solidification method, and their crystalline properties were evaluated using inductively coupled plasma mass spectrometry, X-ray diffraction, scanning electron microscopy, and field-emission electron probe microanalysis. Radioluminescence, photoluminescence, transmittance, scintillation decay, and pulse-height measurements were conducted to assess their scintillation performance. Structural characterization revealed a well-defined eutectic microstructure together with several Ce-rich phases. The results of the effective neutron sensitivity demonstrated that the Ce concentration was effectively optimized based on the effective neutron sensitivity: the sample with 1 mol% Ce exhibited the highest neutron sensitivity (approximately 1.5 times that of a Ce:LiCaAlF₆ single crystal) and a 1.6-times higher neutron-induced light yield, while maintaining a fast effective decay time of 400 ns. These findings suggest that the Ce:CaF₂/LiF eutectic is a promising candidate for high-performance thermal-neutron scintillators for applications in nuclear decommissioning.