Crystal growth and VUV luminescence properties of Er3+- and Tm3+-doped LiCaAlF6 for detectors (original) (raw)
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Luminescence Mechanism in Doubly Doped rmLaF3{\rm LaF} _{3}rmLaF3:Er,Nd VUV Scintillator
IEEE Transactions on Nuclear Science, 2010
Doubly doped LaF 3 :Er, Nd scintillation crystals were grown by modified micropulling-down method. The Er codoping was chosen to enhance the energy transfer from the host lattice to the Nd 3+ luminescence center via the 5d-levels of Er 3+ , which can be enabled by the overlap of Er 3+ 5d-4f emission spectrum with the Nd 3+ 4f-5d absorption. However, no relevant energy transfer was found by photo-and radioluminescence spectra measurements. The reasons of no significant positive effect of Er codoping are discussed.
Radiation Measurements, 2016
T h e n s 2-type metal elements (Pb and Sn) doped LiCaAlF6 single crystals were grown by a micro-pulling-down (-PD) method. Pb doped LiCaAlF6 [Pb:LiCAF] crystals showed high transparency and single phase of the LiCAF structure. However, we could not obtain Sn:LiCAF crystals due to the evaporation of SnF2 during the crystal growth. There was an absorption peak around 193 nm in the transmittance spectrum of Pb:LiCAF crystal. In the radioluminescence spectrum of the Pb:LiCAF crystal under X-ray irradiation, two emission peaks around 200 and 830 nm were observed.
Optical Materials, 2009
Ce 1%, 2%, and 3%-doped LiCaAlF 6 (LiCAF) single crystals were grown by the micro-pulling-down method. The crystals were transparent, 2.0 mm in diameter and 30-60 mm in length. Neither visible inclusions nor cracks were observed. Optical properties, including absorption coefficient, and photoluminescence emission spectra were measured. The strong absorption line was observed at 260 nm, and absorption coefficients of this line were proportional to Ce 3+ concentration. Emission due to Ce 3+ 5d-4f transition peaking around 285 nm and 310 nm were observed by 260 nm excitation. Simulating a neutron irradiation, 241 Am 5.5 MeV a-ray was used to excite the samples. After a correction of a quantum efficiency of photomultiplier tube and compared with Li-glass scintillator GS20, light yield of 6600 ph/n, and 41 ns decay were achieved 3% doped.
Luminescence mechanism in doubly Gd, Nd-codoped fluoride crystals for VUV scintillators
Journal of Luminescence, 2016
The Nd-doped, Gd-doped and doubly Nd,Gd-codoped BaLu1.2Y0.8F8 (BaLuYF) and LuF3 single crystals were grown by micro-pulling-down method. Their photoluminescence, radioluminescence and alpha-ray-excited pulse-height spectra were studied in the vacuum-ultraviolet (VUV) region to confirm their possible application as fast VUV scintillators. Complementary photoluminescence measurements in the ultra-violet/ visible spectral region were performed as well. The possibility of scintillation performance improvement by Gd codoping was tested. The overall scintillation efficiency of BaLuYF:Nd1% was comparable to that of the LaF3:Nd8% reference sample and only slight improvement was observed after Gd1% codoping. The positive effect of Gd codoping was confirmed for higher dopant concentrations. This was explained by an energy transfer from the high-energy Gd 3+ 4f 2 G(0)7/2 level to the Nd 3+ 5d state. On the other hand, pulse-height spectra showed degradation of the light yield under alpha-ray excitation, which was explained by introduction of slow components due to Gd codoping. On the other hand, no positive effect of Gd codoping was found for the overall scintillation efficiency of Nd-doped LuF3, despite the same energy transfer process was confirmed. Slight improvement of the light yield under alpha-ray excitation was confirmed.
Growth and optical properties of LiF/LaF3 eutectic crystals
Journal of the European Ceramic Society, 2014
Neutron imaging devices employing a scintillator can be used in various fields, and eutectic crystals can be suitable for the imaging with a fine position resolution of a few hundred m. Since LiF and LaF 3 have different refractive indexes of 1.41 and 1.64 at 300 nm, respectively, the eutectic crystal is expected to behave as a scintillator with light guiding properties. Thus, the optical properties of Ce-doped LiF/LaF 3 eutectic crystal grown by micro-pulling down method were investigated. The light output of LiF/Ce:LaF 3 eutectic crystal was relatively small. The emission peaks at 300 nm originating from Ce 3+ of 5d-4f transition were observed under excitation by UV photons and 5.5MeV alpha rays. Moreover, the photo-luminescence decay time of Ce-doped LiF/LaF 3 eutectic crystal was estimated to be 17 1 ns.
Micro-pulling down method-grown Er3+:LiCaAlF6 as prospective vacuum ultraviolet laser material
Journal of Crystal Growth, 2013
We report the successful growth of trivalent erbium-doped lithium calcium aluminum fluoride (Er 3 þ :LiCaAlF 6 ) using the micro-pulling down method. Several absorption bands were observed at 139 nm (71,942 cm À 1 ), 149 nm (67,114 cm À 1 ), and 162 nm (61,728 cm À 1 ), which can be ascribed to 4f-5d transitions in Er 3 þ . Evaluation of its optical properties using the 157-nm emission of a F 2 laser reveal that it has a 163-nm vacuum ultraviolet fluorescence with 1.3-ms decay time, involving a transition originating from the high-spin state of the 4f 10 5d excited state configuration. This is one of the shortest emission wavelengths from solid-state materials reported at room temperature.
Europium (Eu) doped LiF crystals have been grown by the Edge-defined film fed growth (EFG) technique. The designing and installation of the furnace used for the growth of the crystals have been discussed in detail. In the present study, Eu (Eu 2 O 3) has been doped in LiF in different concentration (0.02-0.2 wt %). X-ray diffractometry (XRD) and Energy Dispersive X-ray (EDX) spectroscopy confirms the incorporation of Eu in LiF. The influence of Eu on LiF has been investigated through photoluminescence (PL), thermoluminescence (TL) and electron para-magnetic resonance (EPR) in as-grown and annealed crystals. PL emission spectra shows the presence of both Eu 3+ and Eu 2+ form in the as-grown crystals which is confirmed by EPR results. Whereas, in annealed crystals, Eu is present predominantly as Eu 2+ form. This suggests that growing crystals at high temperature (∼900 °C) in argon gas atmosphere through EFG technique favours the reduction of Eu 3+ → Eu 2+. This reduction phenomenon has been explained on the basis of charge compensation model. TL study of the LiF: Eu (0.02-0.2 wt %) crystals has been done after irradiation with Co 60 gamma rays. In this study, it has been observed that the TL intensity as well as glow curve structure of LiF: Eu crystals are a strong function of Eu concentration. The maximum TL is observed at Eu concentration of 0.05 wt% at which a well defined glow curve structure with a prominent peak at 185 °C and a small peak at 253 °C. Beyond this concentration (0.05 wt %), TL intensity decreases due to aggregation of defects in the host. The peak at 185 °C in LiF: Eu (0.05 wt %) is certainly due to the presence of Eu 2+ associated defects which is also supported by the PL spectra. It has been observed that Eu doping have a key role in creation of more defect levels which lead to the increased number of electron and hole traps. Further, trapping parameters are analysed using glow curve deconvolution method to have an insight study of TL phenomena. Further, TL glow curve structure of as-grown and annealed crystal are distinct which may be attributed to the nature of defect traps formed inside the LiF.
Growth and characterization of Ce-doped LiCaAlF6 single crystals
Journal of Crystal Growth, 1999
(Ce : LiCAF) single crystals with high transparency were grown by the Czochralski technique from the stoichiometric composition. A foreign material adhering to the surface of the crystals was investigated. The distribution coefficient of Ce> was determined to be 0.01. Ultraviolet pulse generation with output energy 30.5 mJ and slope efficiency 39% was obtained from a Ce : LiCAF laser. 0022-0248/99/$ -see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 -0 2 4 8 ( 9 8 ) 0 0 9 7 4 -9
Optical Materials, 2014
Abstract Eu doped LiSrAlF6 (Eu:LiSAF) crystals with various Eu concentrations were grown by a micro-pulling-down (μ-PD) method and the effects of Eu concentration control on crystal growth and scintillation properties for Eu:LiSAF crystals were investigated as a neutron scintillator. As-grown Eu0.3%:LiSAF crystal had no visible inclusion while milky parts were observed in the crystals with higher Eu contents. The secondary phases with the chemical composition of EuF2 or EuF3 in the Eu:LiSAF matrix were observed for the crystals with high Eu contents while the secondary phase couldn’t be observed in the powder XRD patterns. In the radioluminescence spectra of Eu:LiSAF crystals under α-ray irradiation, emission peaks around 375 nm originated from 5d–4f transition of Eu2+ ion were observed. The light yields systematically increased with an increase of actual Eu contents in the crystals and the decay times were 1490–1620 ns.