Heavy Scintillators Based on Gadolinium-Containing Crystalline Fluorite Solid Solutions Activated by Ce3+ and Pr3+ Ions

In mixed crystals (solid solutions) with the fluorite structure $${\text{C}}{{{\text{a}}}_{{1-x}}}{\text{G}}{{{\text{d}}}_{x}}{{{\text{F}}}_{{2 + x}}}$$ , doped with Ce3+ and Pr3+ ions, efficient energy transfer from the matrix Gd3+ ions to the impurity rare-earth ions has been demonstrated. The process of energy transfer between Gd3+ ions and impurity ions was studied to assess the potential of the gadolinium-containing matrix as a sensitizer for Се3+ and Pr3+ ions in order to create γ-radiation scintillators. The obtained results showed that Gd3+ absorbs γ radiation and X-ray photons, increasing the emission of Се3+ and Pr3+ ions. X-ray luminescence studies with different contents (from 0.3 to 5.0 mol %) of the second matrix component GdF3 in the mixed crystal and a low concentration (0.3 mol %) of rare-earth impurity ions showed that the resonant cross-relaxation mechanism of donor–acceptor energy transfer turns into migration mechanism (through the gadolinium sublattice to the impurity ion) with an increase in the content of donor ions (Gd3+). The obtained amplitude spectra showed an increase in the light yield with increasing the Gd3+ content in the scintillator matrix.