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Luminescence and defect creation processes were studied by the photoluminescence, thermally stimulated luminescence, and electron paramagnetic resonance methods in the UV-irradiated single crystals of undoped YAlO3, containing small amounts of Ce, Mo, and Ti ions as accidental impurities. The luminescence of the electron antisite YAl2+-type centers of different structures was found around 2.45 eV and studied at 4.2-500 K. The luminescence of the Ti3+-related centers (2.03 and 1.73 eV) and Ti4+ centers (2.78 eV) was observed as well. Dependences of the number of the YAl2+-type and Ti3+-related centers on the UV irradiation energy, temperature, and duration, as well as on various crystal heat-treatment procedures were examined. As a result of the photostimulated electron transfer from the O2- ligand ions to Mo4+ and Ti4+ ions, the paramagnetic hole O--type centers and electron Ti3+ and Mo3+ centers are created. The antisite YAl2+-type centers are created due to the photostimulated release of electrons mainly from the Mo3+ centers to the conduction band and their subsequent trapping at the YAl3+ ions located near an oxygen vacancy or a defect at the neighboring Y3+ site. [ABSTRACT FROM AUTHOR]

Photoluminescence, thermally stimulated luminescence and electron spin resonance are studied for a PbWO4 crystal grown by the Czochralski method at Bogoroditsk Technical Chemical Plant, Russia from the melt with a precise tuning of the stoichiometry and co-doped with La3+, Y3+, and Mo6+ ions. Photo-thermally stimulated processes of electron and hole centers creation under selective UV irradiation of the crystal in the 3.5-5.0 eV energy range and 85-205 K temperature range are clarified and the optically created electron and hole centers are identified. The electrons in this crystal are found to be mainly trapped at the (MoO4)2− groups as well as at the (WO4)2- groups located close to single La3+ and Y3+ ions, producing electron (MoO4)3-, {(WO4)3- - La3+} and {(WO4)3- - Y3+} centers. The holes are mainly trapped at the regular oxygen ions O2- located close to La3+ and Y3+ ions associated with lead vacancies, producing the O−(I)-type centers, or to single Mo ions, producing the O−(II) centers. No evidence of single-vacancy-related centers has been observed. The data obtained indicate a small concentration of single (non-compensated) oxygen ( VO) and lead ( VPb) vacancies as the traps for electrons and holes, respectively, which explains more favorable scintillation characteristics of the PbWO4:Mo,La,Y crystal as compared with the earlier studied PbWO4:Mo, La and PbWO4:Mo,Y crystals. [ABSTRACT FROM AUTHOR]

At 4.2-300 K, the steady-state and time-resolved emission and excitation spectra as well as the luminescence decay kinetics in the 10 μs-10 s time range are studied for the undoped and Ce3+-doped single crystals of Y2SiO5 and Lu2SiO5. At low temperatures, a broad intrinsic emission band located at 2.55 eV in Y2SiO5 and 2.58 eV in Lu2SiO5 is observed in the luminescence spectra of all the crystals studied under excitation in the charge-transfer absorption region (with Eexc > 4.2 eV). This emission reveals the slow non-exponential decay kinetics characteristic for tunneling recombination processes. In the slow decay kinetics of the low-temperature luminescence of Ce3+-doped crystals, both the multi-exponential and the non-exponential decay stages are detected. The origin of the defects, responsible for the undesirable slow low-temperature luminescence of the undoped and Ce3+-doped Y2SiO5 and Lu2SiO5 crystals is considered. A new mechanism of the processes, resulting in the appearance of different luminescence decay stages, is proposed. [ABSTRACT FROM AUTHOR]

Characteristics of thermally stimulated luminescence (TSL) are studied for the X-ray irradiated at 4, 80, or 295 K nominally undoped Y2SiO5 and Lu2SiO5 single crystals of different origin, containing traps for holes (Ce3+, Tb3+ ions) and electrons (Eu3+, Mo6+ ions), as well as for the Sm3+-doped Lu2SiO5 crystal. For the first time, the TSL glow curves of these materials are measured separately for the electron (Ce3+-, Tb3+-related) and hole (Sm3+-, Eu3+-related) recombination luminescence. Owing to that, the TSL peaks, arising from thermal destruction of electron centers and hole centers, are separately identified. For some TSL peaks, thermal stability parameters of the corresponding traps are calculated. The results are compared with those obtained for Ce3+-doped Y2SiO5 and Lu2SiO5 crystals. [ABSTRACT FROM AUTHOR]

Absorption, electron spin resonance, and photo- and thermally stimulated luminescence characteristics are studied for single crystalline films (SCFs) of Y2SiO5 : Ce and Lu2SiO5 : Ce prepared by the liquid phase epitaxy method with the use of a PbO-containing flux. They are also compared with the characteristics of the corresponding single crystals (SCs) as well as of the undoped Y2SiO5 and Lu2SiO5 SCFs and SCs. The concentration of stable trivalent Ce3+ ions in various SCFs with different lead and cerium contents is found to be negligible. It is suggested that stable tetravalent Ce4+ ions mainly exist in the SCF due to a large concentration of Pb2+ ions whose excess volume and negative charge can be effectively compensated by relatively small tetravalent Ce4+ ions. Nevertheless, the characteristic Ce3+ emission in the SCFs of Y2SiO5 : Ce and Lu2SiO5 : Ce does appear under photoexcitation in the charge-transfer absorption region (Eexc > 4.2 eV), most probably as a result of the two-photon excitation process. Ce3+ emission is observed under excitation by the ionizing radiation as well and is explained by the recombination of free electrons from the conduction band with Ce4+ ions. [ABSTRACT FROM AUTHOR]

The processes of hole localization in double-doped PbWO4 : Mo,La and PbWO4 : Mo,Y single crystals are studied by continuous wave and pulse electron spin resonance (ESR) and thermally stimulated luminescence (TSL) methods. We show that the holes created by UV irradiation are preferably trapped at the oxygen lattice ions in the vicinity of perturbing defects such as lead vacancies, impurity ions (La, Y, Mo), and other lattice imperfections forming mainly two types of O- centres. The hyperfine structures of their spectra suggest that in the first centre (OI), a hole is trapped near the YPb-VPb and LaPb-VPb pairs (VPb denotes the lead ion vacancy). In the second centre (OII), a hole is probably localized within a [WO4-MoO4]3- complex defect. The recombination of thermally released holes with the electrons stored at different traps, including the oxygen-vacancy related Pb+-WO3 and (MoO4)3- centres, is systematically studied by TSL. The thermal stability parameters are evaluated by ESR and TSL techniques for different O--type defects. [ABSTRACT FROM AUTHOR]

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Defects formation under UV-irradiation in the impurity-induced absorption bands at 4.2 K has been studied for crystals with and without traps for electrons (CsI:Pb and Eu 2+ -doped alkali halides, respectively). In both cases the results have been explained by an electron transfer from the impurity-perturbed halogen ion states, resulting in the appearance of electrons and holes in the crystal. In CsI:Pb, the electrons are trapped by lead ions and the holes are self-trapped. In Eu 2+ -doped crystals, the electrons and the holes recombine with the formation of excitons, whose decay results in the creation of Frenkel defects. [ABSTRACT FROM AUTHOR]

Photo- and thermally stimulated luminescence characteristics, as well as photostimulated defects creation processes are investigated in the 85–510 K temperature range for the Li+ co-doped single crystal of Gd 3 (Ga,Al) 5 O 12 :Ce (GAGG:Ce). The results for GAGG:Ce,Li are compared with the corresponding characteristics of the GAGG:Ce and GAGG:Ce, Mg single crystals of similar host composition. The influence of Li+ and Mg2+ ions on the Ce3+ - related emission band position, temperature dependence of the photoluminescence intensity, efficiency of the Gd3+ → Ce3+ energy transfer, intensity and decay kinetics of the afterglow, and thermally stimulated luminescence characteristics is revealed. The presence of the Ce3+ → Ce4+ conversion in GAGG:Ce,Li is confirmed. The conclusion is made that, unlike GAGG:Ce,Mg, the compensation of the Li+ excess negative charge in GAGG:Ce,Li occurs due to both the Ce3+ → Ce4+ conversion and the effective formation of intrinsic crystal lattice defects. The origin of these defects as well as the origin of the electron and hole trapping centers in the GAGG:Ce,Li crystal are discussed. The defects responsible for the low-temperature TSL glow curve peak can appear in the GAGG:Ce,Li crystal for the Li+ - induced excess volume and excess negative charge compensation. Besides, the Li+ ions can stimulate the formation in the crystal of hole centers which are most probably of the O− - type centers [35]. The O− - Li+ centers will be most probably responsible for the high-temperature peaks, like the O− - Mg2+ centers. Moreover, the lack of positive charge in lattice can stimulate creation of single O− centers with low thermal stability. • Photo- and thermally stimulated luminescence of Gd3(Ga,Al)5O12:Ce single crystals co-doped with Li+ is investigated. • Co-doping with Li + leads to both the Ce3+.→ Ce4+ conversion and the formation of intrinsic defects; • Origin of the Li + -induced crystal lattice defects is considered. • Influence of the Li + co-doping on scintillation characteristics of Gd3(Ga,Al)5O12:Ce is discussed. [ABSTRACT FROM AUTHOR]

The primary objective of materials science is the study of the properties of the existing materials and the development of new ones. In the present day, the use of solid-state lasers abroad has prompted material scientists globally to develop novel or enhance the properties of the existing active gain media. Materials comprising rare earth elements have historically proven effective in scintillation applications. The synthesis of LaLu 1-x Yb x O 3 monodisperse nanopowders with a particle size of 50–62 nm via the Pechini complexing citrate method has been the subject of investigation using electron paramagnetic resonance (EPR) spectroscopy and photoluminescence (PL) measurements. The EPR data indicate that the Yb³⁺ ions predominantly create a single type of center, whereby the Yb³⁺ ion substitutes for the Lu³⁺ ion. The calculated EPR g-factors are estimated to be g 1 = 3.85, g 2 = 2.15, g 3 = 1.55 and the 171Yb isotope hyperfine interaction constants are A 1 = 600 × 10−4 cm−1, A 2 = 700 × 10−4 cm−1, A 3 ≈ 1800 × 10−4 cm−1. The principal values of the g factors and the hyperfine tensors indicate that the Yb site in LaLu 1-x Yb x O 3 nanopowders exhibits orthorhombic symmetry. The PL measurements in the wavelength range of 350–1800 nm, with excitation provided by either a xenon lamp or a diode laser, indicate the presence of a broad emission band, centered at 404 nm, in addition to the well-known emission spectrum in the IR region (920–1100 nm) arising from Yb3+ ions. [ABSTRACT FROM AUTHOR]

The paper contains detailed crystal structure and photoluminescence studies of the Bi3+ and Bi3+-Eu3+ co-doped Gd 3 Ga 5 O 12 (GGG) garnet. The studied materials have been synthesized in the form of microcrystalline powders by the common solid-state reaction method. Precise crystal structure parameters were derived from the X-ray powder diffraction data. Photoluminescence studies were done by the steady-state and time-resolved techniques in the 4.2–400 K temperature range. The studied materials show no UV luminescence caused by electronic transitions of a Bi3+ ion. The observed luminescence in visible is interpreted by excitons localized around Bi3+ ions. In particular, two emission bands located at 2.55 eV (486 nm) and 2.05 eV (605 nm) at 4.2 K were revealed. The main emission band at 2.55 eV is attributed to the triplet relaxed state of excitons localized around single (regular) Bi3+ ions, whereas the weaker band at 2.05 eV is related to some associates of a single Bi3+ ion with a crystal lattice defect. The performed studies for Bi3+-Eu3+ co-doped samples indicate that the energy transfer from Bi3+ to Eu3+ is radiative and is caused by reabsorption of the Bi-related exciton emission by Eu3+ ions. The studied materials were also characterized as a single-phase converting phosphor for near-UV excited white LEDs. The possibility of the emission color tuning from blue to orange-red at UV excitation by the way of changing of Bi3+ and Eu3+ concentrations was shown. [ABSTRACT FROM AUTHOR]

The appearance of the ultraviolet Bi3+-related emission band in the thermally stimulated luminescence (TSL) spectrum is observed around 465 K after selective irradiation of the YAlO 3 :Bi perovskite in the Bi3+-related absorption bands. The excitation spectrum of the TSL glow curve peak at 465 K, activation energies of its creation by photons of different energies, and the dependence of the TSL peak intensity on the irradiation duration are measured. The origin of the optically created electron centers and the mechanisms of photostimulated creation of the electron and hole centers under irradiation in the Bi3+-related absorption bands of YAlO 3 :Bi are discussed. The TSL glow curve peak at 465 K is suggested to appear as a result of electrons release from the electron centers intrinsic to the YAlO 3 lattice and their recombination with the hole Bi4+ centers. The same processes are shown to take place in the X-ray-irradiated YAlO 3 :Bi perovskite. The obtained results are important for possible applications of the investigated material in thermoluminescent dosimetry. • YAlO 3 :Bi3+ demonstrates UV thermally stimulated luminescence (TSL) with a main peak at around 465 K. • The TSL is created by the UV irradiation at about 6.1 eV. • X-ray irradiation produces the same TSL. • TSL appears as a result of electrons release from the electron traps intrinsic to YAlO 3 and their recombination with Bi4+ centers. [ABSTRACT FROM AUTHOR]

Abstract: A brief review of recent results obtained at systematic study of the luminescence and photo-thermally stimulated defect creation processes in various undoped and doped crystals is presented. Origin of the blue—B and two green—G(I) and G(II) emissions is clarified. Various localized exciton states are identified and their decay into defects is found. Origin of the defects, created at the decay of self-trapped and localized exciton states and -related states, is studied both by TSL and ESR methods. The origin of the TSL peaks and the mechanisms of defect creation and recombination processes are discussed. [Copyright &y& Elsevier]

Single crystals of Gd 3 (Ga,Al) 5 O 12 :Ce,Mg with different concentration of Mg2+ ions varying from 0 to 0.029 at.% are investigated by the X-ray diffraction, steady-state and time-resolved photoluminescence, and thermally stimulated luminescence (TSL) methods in a wide temperature range (77–510 K). The origin and structure of the luminescence centers are considered. The influence of Mg2+ ions on the structure of the Ce3+-related excited state, the processes taking place in this state, and the TSL characteristics is clarified. At low temperatures, the photoluminescence optical quenching in close {Ce3+ - Mg2+} pairs is found to be responsible for the light yield reduction accompanied with the acceleration of the luminescence decay kinetics. At room temperature, the luminescence quenching can be additionally caused by the thermal ionization of the 5d 1 excited state of Ce3+ ion, whose probability increases with the increasing Ga content. The conclusion is made that in order to create the fast scintillator with the maximum light yield, the concentration of intrinsic crystal lattice defects in Gd 3 (Ga,Al) 5 O 12 :Ce,Mg should be minimized, the optimum composition of the host should be chosen, and the balance between the concentrations of the doped Mg2+ and Ce3+ ions should be optimised. • Photo- and thermoluminescence and XRD of Gd 3 (Ga,Al) 5 O 12 :Ce,Mg crystals are studied. • Influence of Mg2+ ions on the Ce3+-related luminescence and excited states is clarified. • Optical quenching in close {Ce3+ - Mg2+} pairs results in the light yield reduction and accompanied with acceleration of the Ce3+ luminescence decay kinetics. • Ga3+ ions and intrinsic defects strongly influence the luminescence thermal quenching. • Optimum host composition and preferable Ce3+/Mg2+ concentration ratio are considered. [ABSTRACT FROM AUTHOR]

Characteristics of the intrinsic and Bi3+-related luminescence of YNbO 4 :Bi powders with different Bi contents are studied at 4.2–500 K by steady-state and time-resolved spectroscopy methods. The emission of YNbO 4 :Bi is suggested to be of an exciton origin. The main Bi3+-related emission band (2.53 eV) excited at 4.09 eV is ascribed to the radiative decay of an exciton localized around a single Bi3+ ion. A weak lower-energy (2.41 eV) emission is ascribed to an exciton localized around a dimer Bi3+ center. No emission arising from the 3P 1,0 → 1S 0 transitions of a Bi3+ ion is found. The structure and parameters of the exciton states, responsible for the luminescence of YNbO 4 :Bi, as well as the radiative and nonradiative processes ongoing in these states are clarified. From the dependence of the afterglow intensity on the irradiation energy, the band gap energy of YNbO 4 is estimated to be 5.3–5.4 eV. [ABSTRACT FROM AUTHOR]

Steady-state and time-resolved emission and excitation spectra and the luminescence decay kinetics are studied in the 4.2–500 K temperature range for the blue intrinsic emission and the yellow Bi3+ - related emission of YVO 4 :Bi, LuVO 4 :Bi, and GdVO 4 :Bi microcrystalline powders. It is suggested that the Bi3+ - related absorption (excitation) band, peaking around 3.75 eV, arises from the electronic transition from the ground 1S 0 state of a Bi3+ ion to its excited 3P 1 state located inside the conduction band (CB). The excitation in the Bi3+ - related absorption band is suggested to result in an electron release from the 3P 1 level of Bi3+ into the CB and its subsequent recombination with the hole remained at the Bi3+ ion. As a result, an exciton localized around the single Bi3+ ion is created. The radiative decay of this exciton is accompanied with the Bi3+ - related 2.12–2.19 eV emission. The origin, structure, and parameters of the exciton states, responsible for the luminescence of the Bi3+ - doped vanadates, and the processes taking place in these states are investigated and discussed. No ultraviolet emission arising from the 3P 1,0 - 1S 0 transition of Bi3+ ions is found. From the afterglow excitation spectra, the band gap energy in the investigated vanadates is estimated to be about 4.20–4.25 eV. [ABSTRACT FROM AUTHOR]

Abstract For the first time, an effective photostimulated creation of defects is observed under selective irradiation of the undoped Gd 3 Ga 3 Al 2 O 12 single crystal and the Ce - doped Gd 3 (Ga,Al) 5 O 12 single crystal and epitaxial film in the Gd3+ - related 8S 7/2 → 6I J and 8S 7/2 → 6P J absorption bands. Defects creation processes are investigated by the thermally stimulated luminescence (TSL) method in the 4.2–500 K temperature range. The dependences of the TSL glow curve peak intensity on the irradiation photon energy, irradiation temperature, and irradiation duration are measured and analyzed. The activation energy of the TSL glow curve peaks creation is found to be about 0.02 eV. Possible mechanisms of defects creation under irradiation in the absorption bands of Gd3+ in Gd 3 Ga 3 Al 2 O 12 and Gd 3 (Ga,Al) 5 O 12 :Ce are discussed. Highlights • Crystals and epitaxial films of undoped and Ce-doped Gd 3 (Ga,Al) 5 O 12 are studied. • Intrinsic electron centers are created under irradiation in the Gd3+ absorption bands. • The defects creation processes are investigated by the thermoluminescence method. • The activation energy of the photostimulated defects creation is about 0.02 eV. • The defects are created as a result of the {Gd3+ - > acceptor} energy transfer. [ABSTRACT FROM AUTHOR]

Photoluminescence and thermally stimulated luminescence of Gd 3 (Ga,Al) 5 O 12 :Ce single crystals and epitaxial films co-doped with different concentrations of Mg 2+ ions are investigated in the 77–500 K temperature range under excitation in the 4f - 5d 1 and 4f - 5d 2 absorption bands of Ce 3+ ions. Influence of Mg 2+ ions on the photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the photoluminescence intensity, and the activation energy of luminescence thermal quenching is observed. Co-doping with Mg 2+ is shown to result in a drastic reduction of the afterglow and thermally stimulated luminescence and in a strong shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The Mg 2+ - induced changes in the characteristics of the Gd 3 (Ga,Al) 5 O 12 :Ce, Mg single crystals and epitaxial films are found to be strongly different, and possible reasons of these differences are discussed. [ABSTRACT FROM AUTHOR]

Microcrystalline powders of Bi3+-doped Y 3 Al 5 O 12 and Lu 3 Al 5 O 12 garnets have been studied by the X-ray diffraction, steady-state and time-resolved photoluminescence, and thermally stimulated luminescence methods. The conclusion is made that the excitation spectra of the Bi3+-related visible exciton-like emission of these compounds, which are located in the 4–6 eV energy range, cannot be explained by the charge-transfer transitions between the energy levels of Bi3+ and the conduction or valence band of the host, whose energies exceed 6 eV. To explain the features observed, this emission is suggested to appear due to the photostimulated electron transfer from the ground state of a Bi3+ ion to defect levels located in the band gap, resulting in the creation of temporary pairs of electron centers and hole Bi4+ centers. A hole delocalization from the Bi4+ ion to the neighboring oxygen O2− ion is also suggested, resulting in the creation of the {O− - Bi3+}-type hole center. As a result of the electron recombination with this hole center, the exciton localized around the Bi3+ ion is formed whose radiative decay is accompanied with the visible emission. • Microcrystalline powders of Y 3 Al 5 O 12 :Bi and Lu 3 Al 5 O 12 :Bi are studied by XRD, PL,TSL. • harge-transfer transitions between Bi3+ and conduction or valence band do no occur. • No stable electron and hole centers are optically created in Bi3+-related absorption bands. • Mechanism of photostimulated creation of temporary electron and hole centers is proposed. • Mechanism of Bi3+-related visible exciton-like emission is proposed for such compounds. [ABSTRACT FROM AUTHOR]

Photo- and radioluminescence and thermally stimulated luminescence characteristics of Ce 3+ - doped and Ce 3+ , Mg 2+ co-doped Gd 3 (Ga,Al) 5 O 12 (GAGG) single crystals of similar composition are investigated in the 9–500 K temperature range. The Ce 3+ - related luminescence spectra and the photoluminescence decay kinetics in these crystals are found to be similar. Under photoexcitation in the Ce 3+ - and Gd 3+ - related absorption bands, no prominent rise of the photoluminescence intensity in time is observed neither in GAGG:Ce,Mg nor in GAGG:Ce crystals. The afterglow is strongly reduced in GAGG:Ce,Mg as compared to GAGG:Ce, and the afterglow decay kinetics is much faster. Co-doping with Mg 2+ results in a drastic decrease of the thermally stimulated luminescence (TSL) intensity in the whole investigated temperature range and in the appearance of a new complex Mg 2+ - related TSL glow curve peak around 285 K. After irradiation in the Ce 3+ - related 3.6 eV absorption band, the TSL intensity in GAGG:Ce,Mg is found to be comparable with that in the GAGG:Ce epitaxial film of similar composition. The Mg 2+ - induced changes in the concentration, origin and structure of the crystal lattice defects and their influence on the scintillation characteristics of GAGG:Ce,Mg are discussed. [ABSTRACT FROM AUTHOR]

Temperature dependences of the intensity and decay kinetics of the Ce 3+ - related photoluminescence and characteristics of thermally stimulated luminescence are investigated in the 77–500 K temperature range for the epitaxial films of the multicomponent garnets of the type of Lu 3−x Gd x Ga y Al 5−y O 12 :Ce with Ce content of 0.3–0.7 at. %, where x varies from 0.14 to 3 and y varies from 0 to 3.54. Different methods are used for the determination of energy distances between the excited 5d 1 and 5d 2 levels of Ce 3+ ions and the conduction band (CB) and their applicability is compared. The dependences of the 5d 1,2 – CB energy distances on the multicomponent garnet composition are clarified. The 5d 1 – CB energy distance is found to decrease by about an order of magnitude with the increasing Ga 3+ content. The most drastic decrease, observed at the Ga 3+ content around y ≈ 1.7, is suggested to arise from the change in the Ga 3+ position from the smaller tetrahedral to larger octahedral Al 3+ sites. This effect is explained by the lattice distortion due to the substitution of smaller Lu 3+ and Al 3+ ions by larger Gd 3+ and Ga 3+ ions. Application potential of these epitaxial films for fast 2D-imaging is discussed. [ABSTRACT FROM AUTHOR]

Luminescence characteristics of epitaxial films of Ce 3+ -doped multicomponent garnets of the type of Lu 3− x Gd x Ga y Al 5− y O 12 , where x varies from 0.14 to 3 and y varies from 0 to 3.54, are investigated in the 4.2–400 K temperature range by the steady-state and time-resolved spectroscopy methods. Their dependence on the film composition is clarified. The presence in the same film of different Ce 3+ -related luminescence centers is revealed, and a possible structure of these centers is discussed. The processes of the electron and hole centers creation under irradiation of the films in the Ce 3+ -related absorption bands are studied by thermally stimulated luminescence method. The location of the excited 5d 1 level of Ce 3+ with respect to the bottom of the conduction band and the origin and thermal stability parameters of electron traps in the epitaxial films and in the single crystals of the same composition are found to be different. [ABSTRACT FROM AUTHOR]

The time resolution of scintillation detectors of ionizing radiation is one of the key parameters sought for in the current and future high-energy physics experiments. This study is encouraged by the necessity to find novel detection methods enabling a sub-10-ps time resolution in scintillation detectors and is focused on the exploitation of fast luminescence rise front. Time-resolved photoluminescence (PL) spectroscopy and thermally stimulated luminescence techniques have been used to study two promising scintillators: self-activated lead tungstate (PWO, PbWO 4 ) and Ce-doped gadolinium aluminum gallium garnet (GAGG, Gd 3 Al 2 Ga 3 O 12 ). A sub-picosecond PL rise time is observed in PWO, while longer processes in the PL response in GAGG:Ce are detected and studied. The mechanisms responsible for the PL rise time in self-activated and doped scintillators are under discussion. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) persistent luminescence (afterglow) and thermally stimulated luminescence observed in the 3.6–4.2 eV energy range are studied for microcrystalline powders of the Bi3+-doped Lu 3 Ga 5 O 12 , Y 3 Ga 5 O 12 , and Ca 3 Ga 2 Ge 3 O 12 garnets after their selective UV irradiation at 295 K in the 4–6 eV energy range. Emission and excitation spectra and decay kinetics of the persistent luminescence, as well as the luminescence intensity dependence on the irradiation duration, are measured at 295 K. No UV emission has been observed in the afterglow spectrum of the Gd 3 Ga 5 O 12 :Bi, Lu 3 Al 5 O 12 :Bi, and Y 3 Al 5 O 12 :Bi garnets. The processes resulting in the appearance of the UV persistent luminescence in the investigated Bi3+-doped garnets are discussed. The conditions are formulated which ensure the appearance of this phenomenon in Bi3+-doped compounds and, thus, could inspire the discovery of new effective UV persistent phosphors. • UV persistent luminescence is observed in Lu 3 Ga 5 O 12 :Bi, Y 3 Ga 5 O 12 :Bi, Ca 3 Ga 2 Ge 3 O 12 :Bi. • Afterglow emission and excitation spectra and decay kinetics are studied. • Most intense and long afterglow appears after irradiation in E > 4.8 eV energy range. • Processes resulting in UV persistent luminescence of Bi-doped compounds are discussed. • Conditions are formulated ensuring the appearance of this phenomenon. [ABSTRACT FROM AUTHOR]

Microcrystalline powders of Y 3 Ga 5 O 12 :Bi and Gd 3 Ga 5 O 12 :Bi are investigated by the X-ray diffraction, scanning electron microscopy, time-resolved photoluminescence, and thermally stimulated luminescence methods in a wide temperature range (4.2–500 K). The results are compared with those obtained recently for the Lu 3 Ga 5 O 12 :Bi powder. The presence of the ultraviolet (UV) emission of a Bi3+ ion and the visible (VIS) emission of an exciton localized around the Bi3+ ion is confirmed for all the investigated gallium garnets. The processes of photostimulated creation of electron and hole centers taking place under irradiation in the 4–6 eV energy range are investigated. The origin of the hole centers responsible for the UV and VIS electron recombination luminescence is clarified. Electron transitions between the energy levels of Bi3+ ions and the Bi3+ → Ga3+ oct , Bi3+ → Ga3+ tetr , and Bi3+ → Y3+ or Bi3+ → Gd3+ electron transfer transitions are found to appear in the photo- and thermoluminescence excitation spectra. The Bi3+ energy level positions in the band gap are determined. Their influence on the luminescence and photostimulated creation of electron and hole centers is discussed. • Y 3 Ga 5 O 12 :Bi and Gd 3 Ga 5 O 12 :Bi are studied by XRD, photoluminescence, TSL methods. • Luminescence of Bi3+ ions and excitons localized around Bi3+ ions is identified. • Bi3+.→Ga3+ oct , Bi3+→Ga3+ tetr , Bi3+→RE3+ electron transfer transitions are observed • Electron and Bi4+-, {O− - Bi3+}-type hole centers are created by UV irradiation. • Photoluminescence excitation and defects creation mechanisms are clarified. [ABSTRACT FROM AUTHOR]

Steady-state and time-resolved emission and excitation spectra as well as luminescence decay kinetics are studied at 4.2–400 K under excitation in the 3–6 eV energy range for Bi 3+ ions substituting for Y 3+ ions in four inequivalent crystal lattice sites of Y 4 Al 2 O 9 :Bi ceramics. Luminescence characteristics of Bi 3+ centers of all the four types are identified and are shown to arise from the radiative decay of the triplet relaxed excited state (RES) of Bi 3+ ions. The parameters of the triplet RES, namely, probabilities of the radiative and nonradiative transitions from the metastable and emitting levels as well as the energy distance between these levels, are determined. The influence of the nearest surroundings of Bi 3+ ions on the luminescence characteristics and the parameters of the triplet RES of Bi 3+ centers is discussed. [ABSTRACT FROM AUTHOR]

Thermally stimulated luminescence (TSL) characteristics (TSL glow curves and TSL spectra) are investigated in the 4–520 K temperature range for the single crystals of gadolinium and lutetium–gadolinium oxyorthosilicates X-ray irradiated at 4 K, 8 K, or 80 K. The nominally undoped Gd 2 SiO 5 and (Lu,Gd) 2 SiO 5 crystals, containing traces of Ce 3+ , Tb 3+ , and Eu 3+ ions, and Ce 3+ -doped Gd 2 SiO 5 and (Lu,Gd) 2 SiO 5 crystals are studied. For the first time, the TSL glow curves of these materials are measured separately for the electron (intrinsic, Ce 3+ - or Tb 3+ -related) and hole (Eu 3+ -related) recombination luminescence, and the TSL glow curve peaks, arising from thermal decay of various electron and hole centers, are identified. The origin of the traps related to the TSL peaks is discussed, and thermal stability parameters of the electron and hole traps are calculated. [ABSTRACT FROM AUTHOR]

Abstract: In the temperature range 4.2–350 K, the steady-state and time-resolved emission and excitation spectra and luminescence decay kinetics are studied for the undoped Y2SiO5 and Lu2SiO5 single crystalline films grown by liquid phase epitaxy method from the PbO-based flux and, owing to that, containing lead ions substituting for Y3+ or Lu3+ ions. Luminescence characteristics of Pb-related centers of different types are identified. On the basis of the results obtained, we suggest that the ultraviolet emission of Pb-related centers arises from the Pb2+ ions substituting for Y3+ or Lu3+ ions in the Y1 and Lu1 lattice sites of the X2 structure. Possible hypotheses on the origin of the intense complex lead-related blue emission are discussed. We propose phenomenological models describing the excited-state dynamics of the studied luminescence centers. We also determine characteristic parameters of the corresponding relaxed excited states, in particular, the energy separations between the excited states and the rates of the radiative and non-radiative transitions from these states. [Copyright &y& Elsevier]

Abstract: Single crystalline films of Bi-doped Y2SiO5 are studied at 4.2–350 K by the time-resolved luminescence methods under excitation in the 3.8–6.2 eV energy range. Ultraviolet luminescence of Y2SiO5:Bi (≈3.6 eV) is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi3+ centers which are related to the 3P0 and 3P1 levels of a free Bi3+ ion, respectively. The lowest-energy excitation band of this emission, located at ≈4.5 eV, is assigned to the 1S0 → 3P1 transitions of a free Bi3+ ion. The phenomenological model is proposed to describe the excited-state dynamics of Bi3+ centers in Y2SiO5:Bi, and parameters of the triplet RES are determined. [Copyright &y& Elsevier]

Abstract: In PbWO4 crystals, doped with various trivalent rare-earth A3+ ions (A3+: La3+, Lu3+, Y3+, Ce3+, Gd3+), electron (WO4)3− and {(WO4)3−–A3+} centers can be created under UV irradiation not only in the host absorption region but also in the energy range around 3.85eV (Böhm et al., 1999; Krasnikov et al., 2010). Under excitation in the same energy range, the UV emission peak at 3.05–3.20eV is observed. In the present work, the origin of this emission is investigated in detail by low-temperature time-resolved luminescence methods. Photo-thermally stimulated creation of (WO4)3− and {(WO4)3−–A3+} centers is studied also in PbWO4:Mo,A3+ crystals. Various processes, which could explain both the appearance of the UV emission and the creation of the {(WO4)3−–A3+}-type centers under irradiation of PbWO4: A3+ crystals in the 3.85±0.35eV energy range, are discussed. The radiative and non-radiative decay of the excitons localized near A3+ ions is considered as the most probable mechanism to explain the observed features. [Copyright &y& Elsevier]

Abstract: Single crystalline films of Lu2SiO5:Bi, prepared by the liquid phase epitaxy method from the melt-solution based on Bi2O3 flux, are studied at 4.2–350K by the time-resolved spectroscopy methods under excitation in the 2.4–6.2eV energy range. An intense dominant ultraviolet (≈3.5eV) luminescence of Lu2SiO5:Bi is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi3+ centers which are related to the 3P0 and 3P1 levels of a free Bi3+ ion, respectively. At T<50K, the radiative transitions from the metastable minima mainly take place. Thermally stimulated non-radiative transitions between the metastable and radiative minima of the triplet RES appear at T>50K in the temperature evolution of the emission spectrum and decay kinetics. The excitation bands of the ultraviolet emission, located at 4.2eV, 5.03eV, and 5.95eV, are assigned to the 1S0→3P1, 1S0→3P2, and 1S0→1P1 transitions of a free Bi3+ ion, respectively. The phenomenological model is proposed to describe the excited-state dynamics of Bi3+ centers in Lu2SiO5:Bi. Characteristic parameters of the triplet RES, in particular the energy separation between the excited states and the rates of the radiative and non-radiative transitions from these states, are determined. Much weaker ≈3.3eV emission is ascribed to the Bi3+ ions located in the Lu2 lattice sites. Weak broad ≈2.2eV and ≈2.3eV emission bands are assumed to arise from the Bi3+-related localized excitons. [Copyright &y& Elsevier]

Abstract: Spectral-kinetic characteristics of Gd3+ and Ce3+ luminescence from a series of Ce3+-doped alkali gadolinium phosphates of MGdP4O12 type (M=Li, Na, Cs) have been studied within 4.2–300K temperature range using time-resolved luminescence spectroscopy techniques. The processes of energy migration along the Gd3+ sub-lattice and energy transfer between the Gd3+ and Ce3+ ions have been investigated. Peculiarities of these processes have been compared for MGdP4O12 phosphate hosts with different alkali metal ions. A contribution of different levels from the 6Pj multiplet of the lowest Gd3+ excited state into the energy migration and transfer processes has been clarified. The phonon-assisted occupation of high-energy 6P5/2, 3/2 levels by Gd3+ in the excited 6Pj state has been revealed as a shift of Gd3+ 6Pj→8S7/2 emission into the short-wavelength spectral range upon the temperature increase. The relaxation of excited Gd3+ via phonon-assisted population of Gd3+ 6P5/2 level (next higher one to the lowest excited 6P7/2) is supposed to be responsible for the rise in probability of energy migration within the Gd3+ sub-lattice initiating the Gd3+→Ce3+ energy transfer at T<150K, whereas further intensification of Gd3+→Ce3+ energy transfer at T>150K is explained by the increase in probability of Gd3+ relaxation into the highest 6P3/2 level of the 6Pj multiplet. An efficient reversed Ce3+→Gd3+ energy transfer has been revealed for the studied phosphates at 4.2K. [Copyright &y& Elsevier]

Abstract: Luminescence characteristics of Ce3+- and Pr3+-doped aluminium perovskite (LuAlO3, YAlO3) and garnet (Lu3Al5O12, Y3Al5O12) single crystalline films, prepared by the liquid phase epitaxy method with the use of the PbO-based flux, were investigated by the time-resolved spectroscopy methods in the 80–300 K temperature range. The influence of various lead-related centers on the characteristics of the Ce3+- and Pr3+-related luminescence centers was studied. It was found that the presence of lead-related centers in the single crystalline films results in a decrease of the quantum efficiency and appearance of undesirable slow components in the luminescence decay kinetics. The possibilities of improving the scintillation characteristics of the single crystalline films were considered. [Copyright &y& Elsevier]

Abstract: Time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 150–300K for the green emission of PbWO4:Mo crystals. It was found that the slow (μs–ms) decay component observed under excitation in the defect-related absorption region (around 3.8–3.9eV) arises from the G(II) emission which appears at the tunneling recombination of optically created electron and hole centers. The study of the emission decay kinetics at different temperatures and excitation intensities allowed concluding that both the monomolecular and the bimolecular tunneling recombination process can be stimulated in the mentioned energy range. The monomolecular process takes place in the isolated spatially correlated pairs of electron and hole centers produced without release of electrons into the conduction band. The bimolecular process takes place in the pairs of randomly distributed centers created at the trapping of free electrons from the conduction band. The formation of electron centers under irradiation in the defect-related absorption region was investigated by the electron spin resonance (ESR) and thermally stimulated luminescence (TSL) methods. The possibility of various photo-thermally stimulated defects creation processes, which take place with and without release of free electrons into the conduction band, was confirmed. [Copyright &y& Elsevier]

Abstract: At 4.2–350K, the steady-state and time-resolved emission and excitation spectra and luminescence decay kinetics were studied under excitation in the 2.5–15eV energy range for the undoped and Ce3+-doped Lu3Al5O12 (LuAG) single-crystalline films grown by liquid phase epitaxy method from the PbO-based flux. The spectral bands arising from the single Pb2+-based centres were identified. The processes of energy transfer from the host lattice to Pb2+ and Ce3+ ions and from Pb2+ to Ce3+ ions were investigated. Competition between Pb2+ and Ce3+ ions in the processes of energy transfer from the LuAG crystal lattice was evidenced especially in the exciton absorption region. Due to overlap of the 3.61eV emission band of Pb2+ centres with the 3.6eV absorption band of Ce3+ centres, an effective nonradiative energy transfer from Pb2+ ions to Ce3+ ions takes place, resulting in the appearance of slower component in the luminescence decay kinetics of Ce3+ centres and decrease of the Ce3+-related luminescence intensity. [Copyright &y& Elsevier]

Abstract: Using the methods of time-resolved and steady-state luminescence spectroscopies, the luminescence and defects creation processes were studied at 4.2–300K under excitation in the 3.0–10.5eV energy range for an YAlO3:Ce crystal with very low concentration of Ce3+ ions. The results were compared with those obtained at the study of YAlO3:Ce crystals with large Ce3+ content coming from the same technological laboratory. Three irregular Ce3+ centers were found and two intrinsic defect luminescence centers related to the cation and oxygen vacancies were evidenced. The origin and structure of luminescence centers are discussed. [Copyright &y& Elsevier]

Abstract: Characteristics of two green emission bands, G(I) and G(II), and their origin were investigated within 0.4–300K under photoexcitation in the 3.4–6.0eV energy range for undoped and Mo6+-, Mo6+ , Y3+-, Mo6+, Nb5+-, Mo6+, Ce3+-, Cr6+-, La3+-, Ba2+- and Cd2+-doped PbWO4 crystals with different concentrations of impurity and intrinsic defects, grown by different methods and annealed at different conditions. The G(I) emission band, observed at low temperatures, located around 2.3–2.4eV and excited around 3.9eV, is usually a superposition of many closely positioned bands. The G(I) emission of undoped crystals is assumed to arise from the WO4 2− groups located in the crystal regions of lead-deficient structure. In Mo6+-doped crystals, this emission arises mainly from the MoO4 2− groups themselves. The G(II) emission band located at 2.5eV is observed only in the crystals, containing the isolated oxygen vacancies — WO3 groups. This emission appears at T>160K under excitation around 4.07eV as a result of the photo-thermally stimulated disintegration of localized exciton states and subsequent recombination of the produced electron and hole centres near WO3 groups. The G(II) emission accompanies also thermally stimulated recombination processes in PbWO4 crystals above 150K. Mainly the G(II) emission is responsible for the slow decay of the green luminescence in PbWO4 crystals. [Copyright &y& Elsevier]

Luminescence characteristics of a large number of undoped and doped PbWO4 crystals, grown by the Czochralski or Bridgman method, as-grown or annealed in the nitrogen atmosphere or in air, were studied in the 4.2–300 K temperature range. Two types of red emission centres were found. The centres with the emission band, peaking at 4.2 K at 1.57 eV, were observed in most of the crystals studied. The centres with the emission band, peaking at 4.2 K at 1.48 eV, were observed only in the PbWO4 : Mo6+, Y3+ crystal. It is suggested that incompletely compensated lead vacancies are responsible for the appearance of the red emission. [Copyright &y& Elsevier]

Luminescence characteristics of a number of undoped and variously doped PbWO4 crystals were studied at 0.4–400 K by the time-resolved spectroscopy and compared with those of ZnWO4,CdWO4 and PbMoO4 crystals. Two types of green emission centres are detected in PbWO4 crystals. The centres of the first type are responsible for the low-temperature 2.3–2.4 eV emission observed under excitation around 3.90–3.95 eV. The structure and parameters of their relaxed excited states were determined. It was concluded that the origin of defects responsible for the green emission of the first type could vary for different crystals. The centres of the second type with the emission around 2.5 eV appear in crystals containing oxygen vacancies after the thermal destruction of Pb+-WO3 centres at T>180 K. Decomposition of the exciton and various defect-related states was also studied, and activation energies of this process were calculated. [Copyright &y& Elsevier]

Emission, excitation and polarization spectra and luminescence decay kinetics have been studied for CsI:Tl single crystals with different thallium concentrations, and the spectral bands of complicated thallium centres separated. The 2.75 eV emission has been ascribed to triplet emission from dimer Tl+Tl+ centres. A similar emission band has been found in polycrystalline CsI:Tl layers and is assumed to be responsible for some important characteristics of the CsI:Tl scintillator. In this paper we give an explanation of these centres and the proposed correlation of the light yield with the thallium dimer centres. [Copyright &y& Elsevier]

Luminescence spectral and kinetic characteristics have been studied under the synchrotron excitation in the energy range of 4–20 eV for CsPbCl3 microcrystals dispersed in a PbCl2 crystal matrix. In the luminescence decay kinetics of the CsPbCl3 microcrystals, different components have been recorded and connected with the direct excitation of the microcrystals and reabsorption of the self-trapped exciton emission of a PbCl2 matrix. The decrease of the luminescence decay time of the CsPbCl3 microcrystals as compared with that characteristic of a CsPbCl3 single crystal may be caused by the quantum size effect. [Copyright &y& Elsevier]

Microcrystalline powders of LuNbO 4 :Bi3+, Eu3+ with the same nominal Bi3+ concentration (2 at.%) and different nominal Eu3+ concentrations (varying from 0 to 8 at.%) are synthesized and analyzed by the X-ray diffraction method. Photoluminescence characteristics of the co-doped LuNbO 4 :Bi, Eu powders are investigated by the steady-state and time-resolved luminescence spectroscopy methods in a wide temperature range (4.2–500 K) and compared with those of the undoped and bismuth-doped LuNbO 4. It is found that owing to the overlap of the intrinsic and Bi3+-related emission bands with the absorption bands of Eu3+, an effective non-radiative (resonance) energy transfer from both the host and the Bi3+-related exciton-like states to Eu3+ ions, resulting in the appearance of the luminescence in the 1.6–3.8 eV energy range, takes place in LuNbO 4 :Bi, Eu. The exchange interaction is found to be responsible for the energy transfer process. The possible application of LuNbO 4 :Bi, Eu in white light-emitting diodes is discussed. LuNbO 4 :Bi3+, Eu3+ powders with different Eu3+ concentration are synthesized. The powders are studied by XRD and time-resolved luminescence methods. Non-radiative energy transfer from Bi3+-related excitons to Eu3+ is revealed. Exchange interaction is responsible for the energy transfer in LuNbO 4 :Bi3+, Eu3+. The LuNbO 4 :Bi3+, Eu3+ compound can be suitable for application in WLEDs. [ABSTRACT FROM AUTHOR]

Photoluminescence characteristics of the undoped and Bi3+-doped lanthanide niobates are investigated by the steady-state and time-resolved spectroscopy methods in a wide temperature range of 4.2–500 K. The broad visible emission bands with the large Stokes shifts are found to arise from the triplet relaxed excited states characterized by a small (∼1 meV) spin-orbit splitting energy. This indicates the exciton-like origin of all the observed emission bands. The data allow to conclude that the Bi3+-related triplet relaxed excited state is located inside the conduction band. No ultraviolet emission caused by the radiative decay of the triplet relaxed excited state of a Bi3+ ion is observed. The dependences of the emission intensity on the Bi3+ content indicate that the complex visible emission band of the Bi3+-doped niobates consists of two main, the higher-energy and the lower-energy, components arising from the excitons localized around the single Bi3+ ions and the {Bi3+ - Bi3+} dimers, respectively. The processes resulting in the appearance of the exciton-like emission under photoexcitation in the Bi3+-related absorption bands are discussed. • LuNbO 4 :Bi and GdNbO 4 :Bi powders are synthesized and analyzed by XRD. • Intrinsic and Bi3+-related luminescence of Bi3+-doped lanthanide niobates is studied. • Triplet luminescence of Bi3+ ions is absent in YNbO 4 :Bi, LuNbO 4 :Bi and GdNbO 4 :Bi. • Emission of excitons localized around single and dimer Bi3+ centers is found. • Structure and parameters of the corresponding exciton-like states are determined. [ABSTRACT FROM AUTHOR]

Abstract: Emission and excitation spectra and luminescence decay kinetics were studied for Pr3+-doped Lu3Al5O12 and Y3Al5O12 single crystalline films (SCF) grown by the liquid phase epitaxy method from a PbO-based flux. The influence of lead-induced centers on their scintillation characteristics was clarified. It was found that the influence of single Pb2+-based centers on the characteristics of Pr3+ centers due to the Pb2+ →Pr3+ energy transfer was weak. However, an overlap of the emission spectra of single and dimer lead-induced centers with the emission spectrum of Pr3+ ions, and especially a strong overlap of the 4f–5d1 absorption band of Pr3+ ions with the slow emission of localized excitons in the 290nm band had a considerable influence on the scintillation characteristics of the Pr3+-doped SCF. [Copyright &y& Elsevier]

Abstract: The steady-state and time-resolved emission and excitation spectra as well as defects creation spectra were studied for Pr3+-doped Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) single crystals at 11–300K in the 2–12eV energy range. For Pr3+-related UV emission bands located at 3.0–4.2eV and excited in the band-to-band and exciton absorption regions, additional excitation bands are observed around 6.9–6.35eV (LuAG) and 6.7–6.25eV (YAG), which are absent in the undoped crystals and in the excitation spectrum of the intrinsic emission. The wide intrinsic emission observed at 11K around 4.9eV, arising from the antisite defects , is excited only in the exciton band and in the band-to-band absorption region. [Copyright &y& Elsevier]

Abstract: Emission and excitation spectra and decay kinetics are studied for the luminescence of undoped and Ce3+-doped LuScAG and LuYAG crystals at 10–300K and compared with the characteristics of undoped and Ce3+-doped YAG and LuAG. Besides the Ce3+-related intense green emission bands, the intrinsic UV bands are observed. At 80K they are located at 4.9-4.4eV. At RT the intrinsic emission bands are located at lower energies. The positions of the lowest-energy excitation band of the intrinsic emission in all the crystals studied are different and shifted to lower energies with respect to that in LuAG (7.2eV at 80K). This band is ascribed to the exciton perturbed by the corresponding defect (Lu3+, Y3+, Sc3+, Ce3+). The origin of the Sc3+- and Y3+-related luminescence and the role of these ions in the processes of energy transfer from the crystal lattice to Ce3+ ions are discussed. [Copyright &y& Elsevier]

Photoluminescence and thermally stimulated luminescence of Ce3+ - doped (Lu,Gd) 3 (Ga,Al) 5 O 12 epitaxial films co-doped with different concentrations of Mg2+ ions (varying from 0 to 0.09 at.%) are investigated in the 60–500 K temperature range under selective photoexcitation in the Ce3+ - related 4f → 5d 2 and 4f → 5d 1 absorption bands and in the absorption bands arising from the 8S 7/2 →6I J and 8S 7/2 →6P J electronic transitions of Gd3+ ions. Influence of Mg2+ ions on the Ce3+ - related photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the emission intensity, and the activation energy of the luminescence thermal quenching is studied. The shortening of the luminescence decay time and simultaneous reduction of its light yield are explained by the presence of {Ce3+ - Mg2+} centers in the Mg2+ - containing films, where the luminescence optical quenching occurs in the 5d 1 excited state of Ce3+ in these centers. Co-doping with Mg2+ results in the reduction of the afterglow and thermally stimulated luminescence and shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The optimum Mg2+ content in the (Lu,Gd) 3 (Ga,Al) 5 O 12 :Ce epitaxial films is estimated to be around 0.005 at.%. • The presence of {Ce3+-Mg2+} centers in (Lu,Gd) 3 (Ga,Al) 5 O 12 :Ce,Mg is suggested. • Optical quenching of {Ce3+-Mg2+} emission takes place in their 5d 1 excited state. • This explains the decrease of their luminescence light yield and decay time. • Mg2+ co-doping reduces TSL and afterglow intensity. • Mg2+ co-doping influences the activation energy and spectra of defects creation. [ABSTRACT FROM AUTHOR]