Charge Transfer Luminescence of LiCa3MgV3O12 and LiCa3ZnV3O12 Under Ionizing Radiation Excitation

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A scintillator is a material that generates a large number of excited electrons and holes under ionizing radiation excitation and immediately emits light with recombination of electrons and holes. When a scintillator combined with a photodetector, it is used as a radiation detector. Radiation detectors equipped with scintillators are applied in various fields such as medical care, security, and radiation protection. Researches are still being conducted to find novel materials with higher performance. In particular, we are attracted to compounds containing lithium (Li). This is because the Li isotope 6Li causes a nuclear reaction with neutrons, so Li-containing materials could be used as neutron scintillators. The Ce-doped lithium silicate glass (lithium glass) and the Eu-doped LiI single crystal are known as conventional Li-containing scintillators; however, the segregation of dopants in these materials can be a problem. For example, the lithium glass can be divided into areas with high and low emission intensity by the dopant segregation. It causes a double-peak in the pulse height spectra under neutron irradiation, and measurement accuracy will deteriorate. In this study, we focused on LiCa3MgV3O12 and LiCa3ZnV3O12 as candidates for scintillators that contain Li and do not require dopants. The photoluminescence properties of powder samples of LiCa3MgV3O12 and LiCa3ZnV3O12 have already been reported; however, scintillation properties have not yet been investigated. We prepared the sintered ceramics of LiCa3MgV3O12 and LiCa3ZnV3O12 and evaluated their scintillation properties. High-purity powders of Li2CO3, CaO, MgO, ZnO, and V2O5 were used as raw materials. They were weighed in stoichiometric proportions and ground using aluminum mortar and pestle, and then calcined at 750℃ for 6 hours in aluminum crucibles. The obtained powders were ground again, pressed into pellets, and then sintered at 850℃ for 6 hours. The X-ray diffraction (XRD) patterns of the samples were measured and compared with those in the previous literature, and we confirmed that each of them had a single phase. In the X-ray induced scintillation spectra, broad luminescence peaking at around 500 nm was observed in each sample. Both emissions can be explained by the charge transfer transition between V5+–O2-.