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Luminescence and scintillation properties of single crystalline films (SCF) of Ce-and Pr-doped Y 3 Al 5 O 12 (YAG) and Lu 3 Al 5 O 12 (LuAG) garnets were analysed and compared with their bulk single crystal (SC) analogues. It was shown that the main peculiarities of luminescent properties of Ce-and Pr-doped YAG and LuAG SCF are due to the absence of Y Al and Lu Al antisite defects (AD) and to the extremely low concentration of vacancy-type defects in SCF with respect to SC. In SCF the absence of the AD-related traps results in faster energy transfer to the emission centres and accelerated scintillation response.

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Single-crystalline films of Lu(3)Al(5)O(12):Bi, prepared by the liquid phase epitaxy method from the melt-solution based on Bi(2)O(3) flux, have been studied at 4.2-400 K by time-resolved luminescence spectroscopy methods. Their emission spectra consist of two types of bands with strongly different characteristics. The ultraviolet emission band consists of two components, arising from the electronic transitions which correspond to the [Formula: see text] and [Formula: see text] transitions in a free Bi(3+) ion. At low temperatures, mainly the lower-energy component of this emission is observed, having the decay time∼10(-3) s at T<100 K and arising from the metastable (3)P(0) level. At T>100 K, the higher-energy emission component appears, arising from the thermally populated emitting (3)P(1) level. The visible emission spectrum consists of two dominant strongly overlapped broad bands with large Stokes shifts. At 4.2 K, their decay times are ∼10(-5) s and decrease with increasing temperature. Both of the visible emission bands are assumed to have an exciton origin. The lower-energy band is ascribed to an exciton, localized near a single Bi(3+) ion. The higher-energy band shows a stronger intensity dependence on the Bi(3+) content and is assumed to arise from an exciton localized near a dimer Bi(3+) center. The origin and structure of the corresponding excited states is considered and the processes, taking place in the excited states, are discussed.

a b s t r a c tSingle crystalline films of Lu 3 Al 5 O 12 :Bi and Y 3 Al 5 O 12 :Bi have been studied at 4.2-450 K by the timeresolved luminescence spectroscopy method. Their emission spectrum consists of two types of bands with strongly different characteristics. The ultraviolet band consists of two components, arising from the electronic transitions which correspond to the 3 P 1 / 1 S 0 and 3 P 0 / 1 S 0 transitions in a free Bi 3þ ion. At T < 80 K, mainly the lower-energy component with the decay time w10 À3 s is observed, arising from the metastable 3 P 0 level. At T > 150 K, the higher-energy component prevails, arising from the thermally populated emitting 3 P 1 level. The visible emission spectrum consists of two dominant strongly overlapped broad bands with large Stokes shifts. At 4.2 K, their decay times are w10 À5 s and w10 À4 s and decrease with increasing temperature. Both of the visible emission bands are assumed to be of an exciton origin. The lower-energy band is ascribed to an exciton, localized near a single Bi 3þ ion. The higherenergy band, showing a stronger intensity dependence on the Bi 3þ content, is assumed to arise from an exciton, localized near a dimer Bi 3þ center. The structure of the corresponding excited states is considered, and the processes, taking place in these states, are discussed.

Steady‐state emission and excitation spectra and luminescence decay kinetics were studied at 80–300 K under excitation in the 2.5–6.0 eV energy range for undoped and Ce3+‐doped aluminium garnet (Lu3Al5O12, Y3Al5O12) and aluminium perovskite (LuAlO3, YAlO3) single crystalline films (SCF) grown by Liquid Phase Epitaxy method from the PbO‐based flux. The aim of the work was to identify spectral bands, arising from lead‐induced centers of different types, and to clarify their influence on scintillation characteristics of Ce3+ centers. It was found that in the perovskite SCF studied, the concentration of single Pb2+‐based centers is comparatively small. In the SCF of garnets, in YAG SCF their concentration is considerably smaller than in LuAG SCF. The lead‐induced emission at about 3.1–3.2 eV excited around 3.9 eV was observed in all the SCF studied and ascribed to the dimer lead centers of the type of {Pb2+ – oxygen vacancy – Pb2+}. In Ce3+‐doped perovskite SCF, due to a strong overlap of the excitation band of the dimer centers and the emission band of Ce3+ centers, a considerable influence of dimer lead centers on the scintillation characteristics of these materials is expected. In the SCF of garnets, the influence of dimer lead centers on the characteristics of Ce3+ centers is negligible. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Luminescent properties and the energy transfer from host to Ce 3+ ions are analyzed in single crystalline films (SCF) of YAlO 3 :Ce (YAP:Ce), Y 1−x Lu x AP:Ce (YLuAP:Ce) and LuAlO 3 :Ce (LuAP:Ce) perovskites in comparison with their single crystal (SC) analogues using the timeresolved luminescence spectroscopy under synchrotron radiation excitation. It is shown that the main peculiarity of luminescent properties of YAP:Ce, YLuAP:Ce and LuAG:Ce SCF is determined by the extremely low concentration of Y Al and Lu Al antisite defects and vacancy-type defects in SCF as compared to SC. The advantages of phosphors based on (Y-Lu)AP:Ce SCF are due to the absence of emission and trapping centers in these SCF which are connected with the above mentioned bulk crystal defects.

Bi-doped Lu3Al5O12 (LuAG) single crystalline films (SCFs) of thickness within 8–31 µm were grown by the liquid-phase epitaxy method onto Y3Al5O12 (YAG) single crystal substrates using a melt solution based on a Bi2O3 flux. Their characteristics were compared with YAG : Bi SCFs grown at the same conditions. The concentration of Bi3+ ions in LuAG : Bi and YAG : Bi SCFs was varied by changing the growth temperature in the ranges 0.05–0.18 at% and 0.13–0.57 at%, respectively. The absorption, luminescence and scintillation properties of these SCFs noticeably depend on the Bi3+ concentration. Luminescence spectra of both LuAG : Bi and YAG : Bi SCF consist of two broad emission bands in the UV and visible (VIS) spectral ranges peaking at 4.155–4.085 eV and 2.45–2.66 eV, respectively. Both the UV and VIS luminescence show complex non-exponential decays. Under 241Am α-particle excitation the photoelectron yield of the best performing LuAG : Bi (0.18 at%) and YAG : Bi (0.13 at%) SCFs is about 15% and 21%, respectively, of that of the reference YAP : Ce single crystal.