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The scintillation characteristics of Lu0.8Gd2.2 (Al5– x Ga x )O12:Ce,Mg ( $x = 2.6$ and 3) single crystals grown by the micropulling down method are investigated. The light yield of 27600 photons/MeV obtained for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg is higher than that of 25 400 photons/MeV obtained for Lu0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. The photoluminescence and scintillation decays measured at room temperature (RT) for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg are faster than those for Lu0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. Temperature dependence of radioluminescence (RL) intensity indicates a lower quenching temperature for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg. Coincidence time resolution of a Lu0.8Gd2.2Al2Ga3O12:Ce,Mg detector in coincidence experiment with a BaF2 detector was measured to be 410 ps. The afterglow and thermally stimulated luminescence (TSL) characteristics below RT are also measured.

Scintillation characteristics of Y0.8Gd2.2 (Al5– x Ga x )O12:Ce,Mg ( $x = 2.6$ and 3) single crystals are presented. At 662-keV $\gamma $ -rays, the light yield of 35 600 photons/MeV obtained for Y0.8Gd2.2Al2Ga3O12:Ce,Mg is higher than that of 32 600 photons/MeV for Y0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. Scintillation decay components of 32.3 ns (52.4%) + 104 ns (47.6%) obtained for Y0.8Gd2.2Al2Ga3O12:Ce,Mg are faster than those of 11.5 ns (5%) + 51.2 ns (69%) + 302 ns (26%) obtained for Y0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. The coincidence time resolution of 336 and 389 ps was obtained, respectively, for Y0.8Gd2.2Al2Ga3O12:Ce,Mg-photomultiplier (PMT) and Y0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg-PMT, in coincidence experiment with a BaF2-PMT detector. The radioluminescence yield at room temperature (RT) is comparable for both crystals while the yield below 130 K is about 20% higher for Y0.8Gd2.2Al2Ga3O12:Ce,Mg. Afterglow and thermally stimulated luminescence (TSL) below RT are also measured.

The scintillation properties of Mg2+-codoped Lu0.6Gd2.4Al2Ga3O12:Ce (LGAGG:Ce,Mg) single crystal grown by Czochralski’s method are investigated. The light yield (LY), scintillation decay time, and coincidence time resolution are presented in comparison with a GAGG:Ce,Mg reference crystal. The LY of 26 200 photons/MeV obtained for LGAGG:Ce,Mg is lower than that of 39 600 photons/MeV for GAGG:Ce,Mg. Despite a lower LY value, the time resolution of LGAGG:Ce,Mg is comparable to that of GAGG:Ce,Mg due to its faster scintillation decay time. LGAGG:Ce,Mg exhibits a much faster afterglow decay and a lower thermally stimulated luminescence intensity with respect to GAGG:Ce,Mg.

In this work, we investigate α-particle response of oxide single crystal scintillators and related to the nonproportionality of light yield (LY) and intrinsic energy resolution under excitation with γ rays. The LY and energy resolution measurements are performed at 32, 59.5 and 662 keV γ rays and 5.5 MeV α particles. The α/γ ratio for Lu3Al5O12:Pr and Y3Al5O12:Pr with different Pr3+ concentrations and for (Gd,Y)3Al2Ga3O12:Ce and (Lu,Gd)2SiO5:Ce with different host compositions are also determined. The scintillators with high α/γ ratio show good proportionality of LY down to 32 keV γ rays. The correlation between α/γ ratio and intrinsic energy resolution measured with 32, 59.5 and 662 keV γ rays is obtained. Therefore, the nonproportional response and intrinsic energy resolution of scintillators could be characterized using α/γ ratio.

The scintillation characteristics of Gd3Al2Ga3O12:Ce, Li (GAGG:Ce,Li) and Gd3Al2Ga3O12:Ce, Mg (GAGG:Ce,Mg) single crystals were compared. Radioluminescence spectra and photoluminescence decay curves were measured at various temperatures between 77 and 500 K to investigate the thermal luminescence quenching. At 662 keV γ rays, the LY value of 35,400 photons/MeV and energy resolution of 6.9% obtained for GAGG:Ce, Li are superior to those of 24,200 photons/MeV and 9.5% for GAGG:Ce,Mg. Scintillation decays are approximated by a double exponentials with a fast principal decay component of 47 ns (83%) for GAGG:Ce, Mg and 90 ns (86%) for GAGG:Ce,Li. Coincidence time resolution of 282 ps obtained for GAGG:Ce, Mg is better than that of 389 ps for GAGG:Ce,Li. GAGG:Ce, Mg shows a much lower afterglow and thermally stimulated luminescence intensity with respect to GAGG:Ce,Li.

Scintillation properties of Czochralski-grown Gd3(Al5-xGax)O12:Ce (x = 2.3, 2.6, 3.0) single crystals were investigated. With increasing Ga content in garnet host, the radioluminescence band due to 5d1 → 4f emission transition was blue-shifted due to a decrease in the crystal field splitting of the 5 d levels. At 662 keV γ rays, the LY value of 47,000, 55,100 and 51,900 ph/MeV was obtained for Gd3Al2.7Ga2.3O12:Ce, Gd3Al2.4Ga2.6O12:Ce and Gd3Al2Ga3O12:Ce, respectively. In spite of a lower LY value, Gd3Al2.7Ga2.3O12:Ce shows good energy resolution of 4.1% due to its proportionality of LY. The ratio of LY values under excitation with α- and γ-rays (α/γ ratio) was also determined. The fast component decay time with relative intensity of 146 ns (66%), 142 ns (76%) and 112 ns (76%) was measured in the scintillation decay of Gd3Al2.7Ga2.3O12:Ce, Gd3Al2.4Ga2.6O12:Ce and Gd3Al2Ga3O12:Ce, respectively. Good coincidence time resolution of Gd3Al2Ga3O12:Ce is due to a high initial photon emission rate.

Mo co-doped Y0.8Gd2.2(Al5-xGax)O12:Ce (x = 2.6 and 3) multicomponent garnet crystals were grown by the micro-pulling down method and the luminescence and scintillation properties were investigated. The temperature dependences of radioluminescence yield and photoluminescence decay time were measured to investigate the temperature stability of these crystals. Under excitation with 662 keV γ rays at room temperature, Y0.8Gd2.2(Al2.4Ga2.6)O12:Ce,Mo shows a higher light yield of 53,800 ph/MeV whereas Y0.8Gd2.2(Al2Ga3)O12:Ce,Mo shows a faster scintillation decay times of 50 ns (56%) + 275 ns (44%). A decrease of radioluminescence yield at low temperature observed in correlation with an appearance of the large thermoluminescence peaks can be attributed to the localization of charge carriers at shallow traps.

Luminescence and scintillation characteristics of Mg2+-codoped (LuxGd3-x)Al2.4Ga2.6O12:Ce (x = 0.2–0.8) garnet crystals grown by the micro-pulling down method are investigated. The Ce3+ 5d1 → 4f luminescence is blue-shifted with increasing Lu content due to the decrease in crystal field splitting of the 5 d levels. With increasing Lu content, the shortening of scintillation decay time accompanied with a decrease of LY value as measured at room temperature can be explained by thermal ionization of the Ce3+ 5d1 excited state. Co-doping with Mg2+ results in the shortening of scintillation decay time, the reduction of LY value and afterglow intensity. At low temperature the radioluminescence quenching is observed in correlation with large thermoluminescence peaks, which can be attributed to the localization of electrons at intrinsic shallow traps.

The luminescence and scintillation characteristics of Ce3+ - doped Gd3Sc2(Al3-xGax)O12 (x = 1, 2, 3) garnet crystals were investigated. The Ce3+ luminescence was blue-shifted with increasing Ga content due to the decrease of the crystal field strength. A decrease of Ce3+ luminescence intensity and luminescence decay time at high temperature was observed for all samples due to thermal ionization of the Ce3+ 5d1 excited levels. With increasing Ga content the decrease of thermal activation energies, determined from temperature dependence of decay times, was obtained. Both Gd3Sc2Al2GaO12:Ce and Gd3Sc2AlGa2O12:Ce samples exhibited a comparable light yield (LY) value of 24,000 photons/MeV while the latter sample showed faster scintillation decay time of 12 ns (11%) + 56 ns (89%) with respect to those of 55 ns (28%) + 105 ns (72%) for the former sample. An acceleration of scintillation decay time with an expense of LY value was also obtained for the Mg2+-codoped sample. At low temperature a decrease of scintillation yield was observed in correlation with the intense thermoluminescence peaks, attributing to the localization of electrons at intrinsic shallow traps.

The optical and scintillation characteristics of Gd 2 YAl 2 Ga 3 O 12 :Ce and Lu 2 YAl 2 Ga 3 O 12 :Ce single crystals are investigated. At 662 keV γ-rays, light yield (LY) of 37,900 ph/MeV and energy resolution of 7.0% obtained for Gd 2 YAl 2 Ga 3 O 12 :Ce are superior to those of 18,900 ph/MeV and 11.5% obtained for Lu 2 YAl 2 Ga 3 O 12 :Ce. Scintillation decays are measured using the time-correlated single photon counting technique. A fast component decay time of 45 ns with relative intensity of 88% obtained for Lu 2 YAl 2 Ga 3 O 12 :Ce is superior to that of 50 ns (65%) for Gd 2 YAl 2 Ga 3 O 12 :Ce. The linear attenuation coefficient at 662 keV γ-rays is also determined and discussed.

The luminescence and scintillation characteristics of cerium-doped lutetium-gadolinium orthosilicate (Lu x Gd 2−x SiO 5 :Ce; x=0, 0.8, 1.8) single crystals were investigated. At 662 keV γ-rays, the light yield of 29,800±3000 ph MeV −1 obtained for Lu 1.8 Gd 0.2 SiO 5 :Ce is higher than that of 20,200±2000 and 11,800±1200 ph MeV −1 obtained for Lu 0.8 Gd 1.2 SiO 5 :Ce and Gd 2 SiO 5 :Ce, respectively. The fast component decay time of 32, 18 and 17 ns was measured in the scintillation decay of Gd 2 SiO 5 :Ce, Lu 0.8 Gd 1.2 SiO 5 :Ce and Lu 1.8 Gd 0.2 SiO 5 :Ce, respectively. The coincidence time spectra for 511 keV annihilation quanta were measured in reference to a fast BaF 2 detector and time resolution was discussed in terms of a number of photoelectrons and decay time of the fast component. The mass attenuation coefficient for studied crystals at 60 and 662 keV γ-rays was also evaluated and discussed.

The scintillation timing characteristics of (La,Gd)2Si2O7:Ce (GPSLa23.5%:Ce) single crystal were studied and compared with Gd2SiO5:Ce (GSO:Ce) single crystal. The photoelectron yield, scintillation decay times and coincidence time resolution were measured. At 511 keV γ-rays, the photoelectron yield of 10,770 ± 500 phe MeV−1 and energy resolution of 5.4 ± 0.2% obtained for GPSLa23.5%:Ce are much better than those of 3350 ± 160 phe MeV−1 and 7.8 ± 0.3% obtained for GSO:Ce. The scintillation decay time profile was measured by the time-correlated single photon counting technique using a fast-slow coincidence setup. In both materials the comparable rise times of several nanoseconds are present. The fast component decay time of 56 ns with relative intensity of 49% obtained for GPSLa23.5%:Ce is inferior to that of 32 ns(88%) obtained for GSO:Ce. Consequently, the coincidence time resolution of GPSLa23.5%:Ce is slightly worse than that of GSO:Ce. The normalized time resolution was also discussed in terms of a number of photoelectrons and decay time of the scintillation pulse.

The timing characteristics of scintillation response of Czochralski-grown Gd 3 Al 2 Ga 3 O 12 :Ce and Gd 3 Al 2.6 Ga 2.4 O 12 :Ce single crystals were compared. The photoelectron yield, scintillation decay times, and coincidence time resolution were measured. At 662 keV γ-rays, the photoelectron yield of 6200 phe MeV −1 obtained for Gd 3 Al 2 Ga 3 O 12 :Ce is higher than that of 4970 phe MeV −1 obtained for Gd 3 Al 2.6 Ga 2.4 O 12 :Ce, while an inferior energy resolution of the former (7.2% vs. 5.6%) is observed. Scintillation decays are approximated by sum of exponentials with the dominant fast component decay time and its relative intensity of 89 ns (73%) for Gd 3 Al 2 Ga 3 O 12 :Ce and 136 ns (69%) for Gd 3 Al 2.6 Ga 2.4 O 12 :Ce. The coincidence time resolution obtained for Gd 3 Al 2 Ga 3 O 12 :Ce is superior than that of Gd 3 Al 2.6 Ga 2.4 O 12 :Ce. The normalized time resolution was also discussed in terms of a number of photoelectrons and decay characteristics of the light pulse.

The scintillation properties of Gd 3 Al 2 Ga 3 O 12 :Ce 3+ (GAGG:Ce) single crystals grown by the Czochralski method with 1 at% cerium in the melt were investigated and results were compared with so far published results in the literature. The light yield (LY) and energy resolution were measured using a XP5200B photomultiplier. Despite about twice higher LY for GAGG:Ce, the energy resolution is only slightly better than that of LuAG:Ce due to its worse intrinsic resolution and non-proportionality of LY. The LY dependences on the sample thickness and amplifier shaping time were measured. The estimated photofraction in pulse height spectra of 320 and 662 keV γ-rays and the total mass attenuation coefficient at 662 keV γ-rays were also determined and compared with the theoretical ones calculated using the WinXCom program.

Cerium-doped Gd3Al2Ga3O12 single crystals were grown by the Czochralski method with 1 at.% cerium. Absorption, luminescence and scintillation characteristics were investigated. The light yield and energy resolution were measured under 662 keV γ-ray excitation. The characteristic emission band of Ce3+ 5d–4f transition peaking around 525 nm was observed in the photoluminescence of Gd3Al2Ga3O12:Ce. The light yield of 56,100 ph/MeV and energy resolution of 6.8% were obtained for a 5 × 5 × 1 mm3 Gd3Al2Ga3O12:Ce sample. The light yield dependence on the sample height and on the shaping time was also studied and compared with Lu3Al5O12:Ce crystal.

The luminescence and scintillation characteristics of Czochralski-grown (GdxY3-x)Al2Ga3O12:Ce (x = 1,2,3) single crystals are presented. With increasing Gd content in this garnet host, the 5d2 absorption band was blue-shifted while the 5d1 absorption and 5d1 → 4f emission bands were red-shifted due to an increase in the crystal field splitting of the 5d levels. In addition, the luminescence quenching temperature of the Ce3+emission and activation energy for thermal quenching decreased with increasing Gd content. The Gd3+ → Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. At 662 keV γ - rays, the light yield (LY) of 48,600 ph/MeV and energy resolution of 6.5% was measured for a Gd3Al2Ga3O12:Ce crystal. Scintillation decay measurements were performed using the time-correlated single photon counting technique. Superior time resolution of Gd3Al2Ga3O12:Ce is due to its high LY and fast scintillation response. The total mass attenuation coefficients at 60 and 662 keV γ - rays were also determined.

The scintillation characteristics of Czochralski-grown GdLu2Al2Ga3O12:Ce and GdY2Al2Ga3O12:Ce single crystals were compared for $\gamma$ -ray detection. At 662-keV $\gamma$ -rays, light yield (LY) of 30700 photons/MeV obtained for GdLu2Al2Ga3O12:Ce is higher than that of 27200 photons/MeV obtained for GdY2Al2Ga3O12:Ce, while its energy resolution is inferior (14% versus 10.6%) due to a larger nonproportionality of LY. Scintillation decays were measured using the time-correlated single photon counting technique. A fast component decay time of 48 ns with relative intensity of 71% obtained for GdLu2Al2Ga3O12:Ce is superior to that of 106 ns (57%) for GdY2Al2Ga3O12:Ce. The coincidence time spectrum was measured in reference to a fast BaF2 scintillator, and coincidence time resolution was discussed.