Article

The structural and luminescent properties of Lu3Al5O12:Ce3+ + Lu2O3 crystal phosphors prepared by colloid chemical synthesis

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Abstract

The crystal structure and spectral luminescent properties of composite phosphors Lu3Al5O12:Ce3++Lu2O3 synthesised by colloid chemical approach have been studied by means of X-ray and neutron powder diffraction and optical spectroscopy methods. The formation of stable defect structures on the phase boundary between Lu3Al5O12:Ce3+ and Lu2O3 evidenced. A redistribution of optically active Ce3+ ions between initial Lu3Al5O12 and lutetium oxide Lu2O3 phase occurs during the colloid chemical synthesis, resulting in suppression of luminescence intensity. The modification of luminescent properties by Lu2O3 doping in Lu3Al5O12:Ce3++Lu2O3 is drastically different is comparison with Y3Al5O12:Ce3++Lu2O3. The chemical and structural mechanisms of Lu2O3 doping effects on luminescence properties of lutetium and yttrium garnet - based compounds are discussed.

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... Additionally, with the optimal selection of synthesis conditions and an increase in the concentration of added oxide, the luminescence intensity may be significantly enhanced (Fig. 2). At the same time, for the Lu 3 Al 5 O 12 :Ce 3+ /Lu 2 O 3 systems synthesized under similar conditions, a noticeable suppression of the luminescence intensity was observed with an increase in the concentration of the oxide Lu 2 O 3 [10]. ...
... At the same time, the Al-O bond lengths in the tetrahedral oxygen environment weakly depend on the concentration of Lu 2 O 3 to be introduced. This behavior can be explained by formation of the stable defect structure in the oxide sublattice of luminophores under study obtained by the colloid-chemical method [9,10]. ...
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... It has been discovered recently that in the colloid-chemical synthesis of YAG:Ce 3+ with doping of the nanostructured lutetium oxide Lu 2 O 3 , activated by the ions Ce 3+ , as an additional component, the modified crystalline phosphors may be obtained, whose peak of the luminescence band shifts toward the red region of the spectrum up to λ max ∼ 590 nm[9]. Additionally, with the optimal selection of synthesis conditions and an increase in the concentration of added oxide, the luminescence intensity may be significantly enhanced (Fig. 2)[10]. To determine the nature of the influence of structural specific features of the compounds under study on their spectral-luminescent properties, the YAG:Ce 3+ /Lu 2 O 3 samples were investigated using the neutron diffraction. ...
... At the same time, the Al–O bond lengths in the tetrahedral oxygen environment weakly depend on the concentration of Lu 2 O 3 to be introduced. This behavior can be explained by formation of the stable defect structure in the oxide sublattice of luminophores under study obtained by the colloid-chemical method[9,10]. A noticeable difference in the length change of Al– O bonds causes the anisotropic nature of modification of oxygen dodecahedrons around the Y or Lu atoms, which induces distortions of crystallographic environment of the optically active ion Ce 3+ and a redistribution of the luminescence intensity between two relaxation channels: 5 D 1 → 2 F 5/2 and 5 D 1 → 2 F 7/2[11]. ...
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... The XRD pattern of the LuAG:Ce 3+ phosphor is given in Fig. 2b which well fits with the cubic Lu 3 Al 5 O 12 phase (crystalline garnet form) with PDF number of 73-1368 [48]. The diffraction peak positions are related to the cubic garnet structure of the Ia3d symmetry [49]. Crystalline size of the LuAG:Ce 3+ was calculated according to the Debye-Scherrer equation [22] and was found to be 62 nm. ...
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Scintillation detectors in the form of luminescent films on a bulk substrate have been developed and explored. Thin doped garnet films on the basis of Lu<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> were grown on an undoped Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> nonluminescent substrate for the application as X-ray imaging screens in microtomography. The introduction of Lu provided a strong absorption for X-rays and a possibility to reduce the film thickness down to 1 - 2 μm and to achieve a spatial resolution of 0.8 to 1.2 μm. Doped luminescent films of various materials with the thickness adapted to the path length of short-range particles, were grown or deposited on a doped luminescent substrate intended for detecting long-range particles. Such phoswich-detectors are used for radiation monitoring of low-activity nuclides. Ways to improve the operation characteristics of such detection systems are proposed.
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