Single crystal growth and luminescence properties of CeF ₃-CaF₂ solid solution grown by the micro-pulling-down method

(Ce_xCa_1-x)F_2+x single crystal with x = 0.0001 - 0.03 were grown by the μ-PD method. Ce³⁺ doping in CaFa lattice gives rise to characteristic absorption and emission bands, which are governed by the characteristics of the isolated Ce³⁺ -F _i^- C_4v pair centers and small clusters composed from these pairs. With increasing Ce concentration there is a strong increase of the absorption bands related to the cluster centres, but the radioluminescence spectra are always governed by the emission of the isolated Ce³⁺ -F_i^- C_4v pairs without noticeable changes in the emission band shape. Highest radioluminescence intensity is achieved for Ce0.1{%} concentration and above 1{%} of Ce the onset of concentration quenching is observed. Scintillation response is governed by the energy transfer from the CaFa host lattice and even for the Ce3{%} sample the dominant scintillation decay time is about 50{%} longer with respect to the photoluminescence decay time of Ce³⁺ -F_i^- C_4v pair centres. Energy transfer processes and the role of different Ce3+-based centers are discussed.