Scintillation Properties of Ba3RE(PO4)3 Single Crystals (RE = Y, La, Lu)

Abstract

Eulytite-type Ba3RE(PO4)3 (RE = Y, La, and Lu) single crystals were synthesized by the floating zone method, and their scintillation properties were investigated. The powder X-ray diffraction measurement revealed that the single phase of Ba3RE(PO4)3 samples were successfully synthesized. The samples exhibited a luminescence peak due to self-trapped exciton at around 400 nm under vacuum ultraviolet and X-ray irradiation. The X-ray-induced scintillation decay time constants of the samples were several microseconds at room temperature. In the 241Am α-ray irradiated pulse height spectra, all the samples showed a clear full energy peak, and the absolute light yields of the Ba3Y(PO4)3, Ba3La(PO4)3, and Ba3Lu(PO4)3 single crystals were estimated to be 960, 1160, and 1220 ph/5.5 MeV-α, with a typical error of ±10%, respectively. The scintillation light yields of the Ba3RE(PO4)3 have been quantitatively clarified for the first time.

Crystal Growth, Photoluminescence and Radioluminescence Properties of Ce3+-Doped Ba3Y(PO4)3 Crystal

“…By fitting the emission spectrum with multiple peaks, three curves peaked at 345, 370, and 395 nm can be obtained with good fitness (R 2 = 99.98%). Therein, the emission peak at 395 nm is close to the position of the self-trapped exciton recombination reported in pure BYP crystal [27]. Regarding the double-peak emission of 345 and 370 nm, it may originate from the fact that Ce 3+ occupied two types of sites, but the energy difference (2225 cm −1 ) between the two peaks coincides with the general spacing between 2 F 7/2 and 2 F 5/2 levels in Ce 3+ (2200~2600 cm −1 ), which verifies the weak CF for Ce 3+ in the BYP host.…”

“…However, the emission intensities with respect to the 395 nm emission for all samples are almost unaffected, which is generally interpreted as intrinsic luminescence ascribed to the selftrapped excitons and has no relation to the electron population of the lowest Ce-5d energy level. This characteristic emission band has been observed in other orthorhombic phosphate materials like Ba 3 La(PO 4 ) 3 and Ba 3 Lu(PO 4 ) 3 [27,34], and its larger Stokes shifts, longer emission wavelengths, and broadband emission characteristics are consistent with radiation from self-trapped exciton recombination. To further distinguish the emission between the 5d-4f transition of Ce 3+ and the STE recombination, the low-temperature excitation and temperature-dependent emission spectra of BYP:0.007Ce 3+ were measured.…”

“…ted by the double-exponential decay equation, and the values are almost the same (average decay lifetime: 17.5 ns vs. 15.5 ns). The fast decay of 8 ns should be attributed to the energy transfer from the 5d1 level to STEs, while the latter is closely related to intrinsic defects in the matrix lattice, which have been reported in the radioluminescence of pure BYP crystal [27]. In the present work, the annealing of the crystal did not distinctly change the fluorescence lifetime but significantly decreased the fluorescence intensity.…”

“…The bottom of the CB is mainly composed of Yd and Ba-d orbitals. Y. Takebuchi et al [27] reported that the undoped BREP crystals should have optical bandgaps exceeding 6.2 eV, while the Ba3La(PO4)3:Ce 3+ phosphor is further clarified as having a bandgap of 7.21 eV [34]. The theoretically calculated bandgap value (5.324 eV) of BYP in this work is obviously low, which is even lower than the result deduced from the excitation spectra.…”

“…[21][22][23][24][25][26]. Y. Takebuchi et al have reported that the Ba 3 RE(PO 4 ) 3 (RE = Y, La and Lu) crystals showed the intrinsic luminescence peaked at 400 nm under vacuum-UV and X-ray excitation; the X-ray-induced scintillation decay time was several microseconds, and the absolute light yields were estimated to be 960, 1160, and 1220 ph/5.5 MeV under 241 Am α-ray irradiation, respectively [27]. H. Ezawa et al have reported that the undoped and Tb-doped BYP crystals exhibited the STEs and 4f-4f transitions of Tb 3+ luminescence, respectively, and the thermally stimulated luminescence was observable from 0.01 mGy in 1% Tb-doped BYP [28].…”