Cerium-doped lutetium aluminum garnet optically transparent ceramics fabricated by a sol-gel combustion process
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Hui-Li Li Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China
Rong-Jun Xie, Naoto Hirosaki, and Xin Xu Advanced Materials Laboratory, National Institute for Materials Sciences (NIMS), Tsukuba, Ibaraki 305-0044, Japan
Li-Ping Huang Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China (Received 16 December 2005; accepted 10 March 2006)
Nano-sized cerium-doped lutetium aluminum garnet (LuAG:Ce) powders were prepared via a sol-gel combustion process from a mixed solution of metal nitrates, using organic glycine as a fuel. The purified crystalline phase of LuAG:Ce was obtained after calcination at 1000 °C for 2 h. The obtained phosphors were agglomerated and had a foamy-like morphology, consisting of pointed crystallites with uniform size of about 40 nm. Both the photoluminescence and the radioluminescence of the calcined powders showed the same two emission bands, corresponding to transitions from the lowest 5d excited state (2D) to the 4f ground state of Ce3+ (2F5/2, 2F7/2). Using the prepared powders, polycrystalline LuAG:Ce optically transparent ceramics were successfully fabricated at 1850 °C for 10 h under vacuum without sintering aids and annealed at 1450 °C for 20 h in air. The sintered ceramics are transparent with an in-line light transmittance in the visible wavelength range of about 50% and have a uniform microstructure with an average grain size of about 8 m. The radioluminescence of the transparent ceramics is similar to that for calcined powders, except higher in intensity.
I. INTRODUCTION
An inorganic scintillator plays an important role in radiation detection in many sectors of research concerning almost all medical diagnostic imaging modalities that use x-ray or gamma rays, dosimetry, nuclear medicine, high energy physics, airport security inspection, and so on.1–3 In the different applications, the scintillator is essentially a luminescent material that absorbs the highenergy photons (e.g., x-rays or gamma-rays) and then emits visible light.1–3 Recently, interest has increased in lutetium-based
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0183 J. Mater. Res., Vol. 21, No. 6, Jun 2006
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phosphors materials as potential ionizing radiation detectors.4–13 Their high density and high effective atomic number (Zeff) make them especially attractive for such applications. It has been recognized that lutetium aluminum garnet (Lu3Al5O12; LuAG) could serve as a convenient host lattice for activators to form promising scintillators because of its high density (6.73g/cm3, 94% of BGO), high Zeff (60), and other physical properties such as shock resistivity and chemical radiation stability.4–6 This host lattice containing rare-earth ions as luminescent activators in special cerium (Ce3+) has been investigated because the parity-allowed 5d-4f transitions of Ce3+ ion yield fast (nanosecond) optical transi
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