Sol-gel synthesis of cerium-doped yttrium silicates and their luminescent properties
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in Nikl and Romana Kucerkova´ Institute of Physics of AS CR v.v.i., Cukrovarnicka 10, 16253 Prague, Czech Republic
Carla Cannas University of Cagliari, Chemistry Department, S.S. 554 bivio per Sestu, 09042 Monserrato (Cagliari), Italy (Received 15 June 2009; accepted 16 November 2009)
The Ce-doped yttrium ortho- and pyrosilicate powders were prepared in a powder form by the formamide-modified sol-gel method. Crystal structure was checked by x-ray diffraction and sample morphology by transmission electron microscopy measurements. Both ortho- and pyrosilicate pure phases were obtained by the previously mentioned preparation procedure and proper annealing temperature was determined to obtain the maximum scintillation efficiency. Luminescence spectra and decays were measured to better evaluate the source of efficiency losses in the scintillator mechanism of samples heat-treated at lower temperatures. The potential of this preparation method for manufacturing the nanocomposite scintillators was discussed. I. INTRODUCTION
Ce-doped orthosilicates, Y2SiO5 (YSO) and (Lu–Y)2 SiO5 (LYSO), are important materials with large commercial potential. Bulk single crystals of LSO:Ce and LYSO:Ce have the highest figure of merit for scintillators used in positron emission tomography (PET) and potentially other medical imaging techniques.1–3 YSO:Ce powder phosphors are under development for cathode ray tubes and field-emission devices (FED).4,5 Doubly (Ce,Sm)-doped YSO was reported also as a potential storage phosphor.6 For FEDs, YSO:Ce can replace traditional ZnS:Ag blue phosphor due to its higher resistance to saturation and noticeably lower degradation in operation under high current densities in FED.5 Apart from classical solid-state sintering,6 a number of other technological ways have been used to synthetize YSO:Ce-based phosphors, namely spray pyrolysis,7 combustion synthesis,8 hydrothermal,9 and sol-gel10,11 methods. Using pulsed laser deposition, YSO:Ce thin films were prepared and studied.12 In the published studies, particular attention is paid to the relationship between phosphor efficiency, powder morphology, and preparation method. Material degradation is also frequently considered. Despite active research with the orthosilicate host, the preparation and optical/ scintillation characteristics of Ce-doped yttrium pyroa)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0039 J. Mater. Res., Vol. 25, No. 2, Feb 2010
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silicate (Y2Si2O7:Ce) phosphor have not been reported. Recently, Ce-doped lutetium pyrosilicate synthesis and photoluminescence (PL) characteristics were published.13 It is worth mentioning that Ce-doped lutetium pyrosilicate single crystal appeared much more favorable due to considerably diminished afterglow intensity with respect to the orthosilicate analogue,14 which can be of high importance for the previously mentioned powder phosphor applications. Apart from the practical importance, the yttrium silicates
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