Multifunctional Ca(PO)F as a host for radioactive waste immobilization: Am/Eu ions distribution, phosphor characteristics and radiation induced changes.

NaEu:Ca(PO)F is explored as a potential host for radioactive waste immobilization. Since Eu ion is a surrogate of highly radioactive Am ion, the photoluminescence (PL) characteristics of Eu ion helped to investigate the possible distribution of hazardous and radioactive Am ion among the two lattice sites in the matrix. It was observed that Am will prefer to occupy the Ca2-site lattice which has a direct linkage to F atom. From DFT calculation we have found that both Eu and Am ions are following similar trend of distribution into the Ca2-site compared to Ca1-site which has no F atom linkage. The radiation stability of the compound was also investigated by PL study after irradiating it with a Co gamma source with different doses starting from 2 kGy to as high as 1000 kGy. It was observed that radiation induced changes were more surrounding the Ca1-site than in Ca2-site.Considering all the experimental and theoretical observations it is concluded that from radioactive waste immobilization point of view it is more preferable to dope the Am ion into the Ca2 site. The Eu doped compound was also found to be red color emitting phosphor materials with color purity of 95.24%.