Traps and Timing Characteristics of LuAG:Ce3+ Scintillator

Abstract

New materials are studied for fast and heavy scintillators, which are increasingly used and/or demanded in coming medical and industrial applications. Among others, Ce-doped Lu-containing compounds are under study and development, especially LSO:Ce 3+ and LuAP:Ce 3+ crystals. However, the growth of single crystals of these compounds appeared very difficult, especially the latter system has not been offered by any industrial company yet, even if the first papers dealing with this promising scintillator were published in 1995 by several groups [for review, see [1]).Contrary to LuAP perovskite phase, the garnet one Lu 3 Al 5 O 12 (LuAG) appears as rather stable and can be thus grown more easily. LuAG single crystals have a density of 6.73 g/cm 3 (94% of BGO) and the leading fast emission/scintillation decay component is about 50 ns (six times faster than BGO) peaking between 500 and 550 nm (similar spectral region as BGO emission). Despite of the fact that such material can appear as serious competitor of BGO scintillator, little attention was paid to it in the literature up to now [2].This note provides a direct comparison between YAP:Ce 3+ and LuAG:Ce 3+ scintillators grown in the same laboratory 1 ) as for radioluminescence light output, scintillation decay and thermoluminescence characteristics. A correlation between the occurence of thermo-luminescence (TSL) peaks round RT and of very slow components in the scintillation decay of LuAG:Ce 3+ is revealed. Importance of understanding of the nature of such TSL active trapping states and their removal for further optimisation of LuAG:Ce 3+ scintillator is concluded.The experimental apparate used for scintillation and TSL measurements are described elsewhere [3,4]. We have grown YAP:Ce and LuAG:Ce crystals by Czochralski method. For scintillation decay measurements part of the grown ingot was used with polished front faces (about 1 30 Â 15 mm), while for the other measurements polished plates about 1 8 Â 1 mm were prepared. The composition was checked by electron beam excited X-ray analysis, which confirmed the appropriate stoichiometry of the perovskite and garnet phases, respectively. The concentration of Ce ions in the crystals was measured by the same method to be of about 7000 ppm and comparable amount of Ce 3+ centres in both materials were evidenced also from the optical absorption measurements (amplitude of the Ce 3+ -related absorption bands in UV-visible spectral region). The absorption spectrum of LuAG:Ce 3+ features wide Ce 3+ absorption bands around 450, 343 and 217 nm. The lowest Ce 3+ absorption bands coincide with the excitation bands (450 nm and 345 nm) of the Ce 3+ emission peaking round 510±550 nm at room temperature (RT) with the characteristic double peak structure (512 nm and 547 nm) due to the splitting of the Ce 3+ 4f ground state. The same emission appears also under X-ray excitation , see Fig. 1. The same experimental conditions of the radioluminescence measurements in Fig. 1 allowed to compare relative light output in both materials. After ...

Luminescence of dimer lead centers in aluminium perovskites and garnets

“…1 Introduction Single crystals of lutetium-aluminium garnet Lu 3 Al 5 O 12 (LuAG), yttrium-aluminium garnet Y 3 Al 5 O 12 (YAG), lutetium-aluminium perovskite LuAlO 3 (LuAP), and yttrium-aluminium perovskite YAlO 3 (YAP), doped with Ce 3+ ions, have a high density and excellent mechanical and chemical stability, possess an intense and fast emission due to 5d-4f radiative transition of Ce 3+ and have been, thus, considered for fast scintillator applications (see, e.g., [1][2][3][4]). Under excitation of the undoped, meltgrown bulk single crystals (SC) in the band-to-band and exciton energy range, an intense complex slow intrinsic luminescence was observed in the UV spectral range.…”

Bi3+–Ce3+ energy transfer and luminescent properties of LuAG:Bi,Ce and YAG:Bi,Ce single crystalline films

“…The sets of YAG:Bi,Ce and LuAG:Ce,Bi SCF with dimensions of about 11 cm 2 and thickness between 12 and 60 µm were grown on (110) oriented YAG substrates at LOM, Lviv University, using the LPE method from super-cooled melt-solution based on Bi 2 O 3 oxide flux. We did not use any codoping to reduce a significant mismatch between the lattice constants of LuAG SCF (11.884 Å) and YAG substrate (11.999 Å).…”

“…The Ce 3+ doped Y 3 Al 5 O 12 (YAG) and Lu 3 Al 5 O 12 (LuAG) garnets posses an intense and fast emission in the visible (515-530 nm) range due to 5d-4f radiative transition of Ce 3+ ions and have been considered now for different scintillator applications [1][2][3][4]. The Ce-doped YAG and LuAG-based scintillators can be prepared both in the form of bulk single crystals (SC) by the Czochralski or Bridgman methods [1][2][3][4] as well as in the form of single crystalline films (SCF) by the Liquid Phase Epitaxy (LPE) method with the typical thickness of 2-60 m [5][6][7].…”

“…The Ce-doped YAG and LuAG-based scintillators can be prepared both in the form of bulk single crystals (SC) by the Czochralski or Bridgman methods [1][2][3][4] as well as in the form of single crystalline films (SCF) by the Liquid Phase Epitaxy (LPE) method with the typical thickness of 2-60 m [5][6][7]. Apart the traditional scintillation applications for environmental radiation monitoring [7] they can be employed also for imaging screens with high spatial resolution [8][9][10] with some advantages with respect to typical powder phosphorbased screens [11][12][13].…”

Solvothermal synthesis of lutetium aluminum garnet nanopowders: Determination of the optimum synthesis conditions

“…Lutetium aluminum garnet (Lu 3 Al 5 O 12 , LuAG), the heavier analog of the above described YAG, has also been acknowledged as a well qualified host material for laser and scintillator because of its excellent physical and chemical properties such as high density (6.73 g/cm 3 ), high effective atomic number (60), high thermal conductivity (6.6 W m −1 K −1 ), excellent shock resistivity and chemical radiation stability [4][5][6]. Currently, Ce-doped LuAG can be employed in medical imaging equipments in view of its fast response (about 50 ns) [7]. In addition, Tm-, Yb-, Nd-, and Pr-doped LuAG are very promising for microchip laser, neutrino physics or medical imaging [8][9][10][11].…”