This work presents our latest achievements in the development of advanced composite scintillators for simultaneous registration of α-particles and γ-quanta in mixed ionizing fluxes based on single crystalline films (SCFs) of Tb₃Al₃O₁₂ : Ce (TbAG : Ce) garnet and Gd₃Al_2.5Ga_2.5O₁₂ : Ce (GAGG : Ce) single crystal (SC) substrates using the liquid phase epitaxy (LPE) growth method from a melt-solution based on a PbO–B₂O₃ flux. The separation of the signals from the SCF and SC components of such composite scintillators can be realized by means of registration of the difference in the scintillation decay times of SCF and substrate scintillators and can be achieved at a large K = t(SCF)/t(SC) ratio, which is usually above 2. The TbAG : Ce SCFs exhibit relatively fast scintillation response under α-particle excitation with decay times of t_1/e = 344–380 ns and t_1/100 = 3130–3770 ns. Meanwhile, the scintillation response of TbAG : Ce SCFs under α-particle excitation is significantly slower in the 500–4000 ns range than that of the GAGG : Ce crystals with decay times of t_1/e = 270–280 ns and t_1/20 = 1280–1300 ns. We have found that for TbAG : Ce/GAGG : Ce composite scintillators, the optimal K ratio changes from 2.0 to 3.0 at the registration of scintillations with shaping times of 700–4000 ns. For this reason, TbAG : Ce/GAGG : Ce composite scintillators possess the best scintillation properties among all known LPE grown analogues for simultaneous registration of α-particles and γ-quanta in mixed fluxes.

This manuscript summarizes recent results on the development of composite luminescent materials based on the single-crystalline films and single crystals of simple and mixed garnet compounds obtained by the liquid-phase epitaxy growth method. Such composite materials can be applied as scintillating and thermoluminescent (TL) detectors for radiation monitoring of mixed ionization fluxes, as well as scintillation screens in the microimaging techniques. The film and crystal parts of composite detectors were fabricated from efficient scintillation/TL materials based on Ce³⁺-, Pr³⁺-, and Sc³⁺-doped Lu₃Al₅O₁₂ garnets, as well as Ce³⁺-doped Gd_3−xA_xAl_5−yGa_yO₁₂ mixed garnets, where A = Lu or Tb; x = 0–1; y = 2–3 with significantly different scintillation decay or positions of the main peaks in their TL glow curves. This work also summarizes the results of optical study of films, crystals, and epitaxial structures of these garnet compounds using absorption, cathodoluminescence, and photoluminescence. The scintillation and TL properties of the developed materials under α- and β-particles and γ-quanta excitations were studied as well. The most efficient variants of the composite scintillation and TL detectors for monitoring of composition of mixed beams of ionizing radiation were selected based on the results of this complex study.

The growth of single crystalline films (SCFs) with excellent scintillation properties based on the Tb_1.5Gd_1.5Al_5−yGa_yO₁₂:Ce mixed garnet at y = 2–3.85 by Liquid Phase Epitaxy (LPE) method onto Gd₃Al_2.5Ga_2.5O₁₂ (GAGG) substrates from BaO based flux is reported in this work. We have found that the best scintillation properties are shown by Tb_1.5Gd_1.5Al₃Ga₂O₁₂:Ce SCFs. These SCFs possess the highest light yield (LY) ever obtained in our group for LPE grown garnet SCF scintillators exceeding by at least 10% the LY of previously reported Lu_1.5Gd_1.5Al_2.75Ga_2.25O₁₂:Ce and Gd₃Al_2–2.75 Ga_3–2.25O₁₂:Ce SCF scintillators, grown from BaO based flux. Under α-particles excitation, the Tb_1.5Gd_1.5 Al₃Ga₂O₁₂:Ce SCF show LY comparable with that of high-quality Gd₃Al_2.5Ga_2.5O₁₂:Ce single crystal (SC) scintillator with the LY above 10,000 photons/MeV but faster (at least by 2 times) scintillation decay times t_1/e and t_1/20 of 230 and 730 ns, respectively. The LY of Tb_1.5Gd_1.5Al_2.5Ga_2.5O₁₂:Ce SCFs, grown from PbO flux, is comparable with the LY of their counterparts grown from BaO flux, but these SCFs possess slightly slower scintillation response with decay times t_1/e and t_1/20 of 330 and 990 ns, respectively. Taking into account that the SCFs of the Tb_1.5Gd_1.5Al_3–2.25Ga_2–2.75O₁₂:Ce garnet can also be grown onto Ce³⁺ doped GAGG substrates, the LPE method can also be used for the creation of the hybrid film-substrate scintillators for simultaneous registration of the different components of ionization fluxes.