| Scintillators are widely used in radiation detectors for medical diagnostics, industrial inspection, nuclear medicine, and high-energy physics (HEP) applications. Requirements for scintillator crystals include high effective atomic number (Z), high proportional light yield, fast decay and high transparency. The increased demanding for more ideal scintillator materials has directed interest toward lutetium compounds, because they are characterized by high absorption coefficients for any kind of high-energy ionizing radiation resulting from high density of Lu element. Ceramic scintillators are a new kind of functional materials. Transparent Lu3Al5O12:Ce(LuAG:Ce) ceramic scintillators fabricated through solid-state reaction method has been used in medical PET and SPECT, whereas europium-doped Lu2O3 ceramic scintillator is finding application in the field of digital X-ray imaging technology. However, due to relatively high cost of lutetium compounds and the strigent processing method required to fabricate transparent ceramics, the wider application of lutetium compounds as scintillator materials has been greatly restricted. This thesis is deemd to fabricate scintillators of lutetium compounds, in forms of both powders and transparent ceramics, with lower cost by using nano techniques. Lutetium compounds of Lu2O3, (Lu,Gd)2O3, as well LuAG, were fabricated and their properties were investigated.Nano-sized Lu2O3 powders were synthesized with a precipitation technique using optimized processing parameters. The precursor powders prepared by precipitation technique with ammonium hydrogen carbonate (NH4HCO3) as precipitator were indexed to lutetium normal carbonate and a few basic carbonates. The chemical formula of the precursor is Lu2.1(OH)0.1(CO3)3.1·6H2O. The average particle size was～20nm with spherical morphology. Powders with a primary particle diameter of～35nm were produced by calcining the precursor powders at 800℃for 4 h. Translucent Lu2O3 ceramic scintillators were fabricated by vacuum sintering at 1700℃for 5h.The synthesis of nano-sized powders of Gd(1.9-x)LuxEu0.1O3 solid-solution using the co-precipitation method was investigated. The precursor powders composed of lutetium gadolinium normal carbonate(x=0), or lutetium gadolinium normal carbonate and a few basic carbonates(x= 0.2,0.5,1.0,1.5,1.9), depending on the compositions. The chemical formula may be Gd(1.9-x)LuxEu0.1(OH)0.1x(CO3)(3-0.05x)·6H2O. The powders with low lutetium contents are mainly composed of nanorods, with the aspect ratios decreasing gradually with increasing of Lu2O3 composition. The powders with high lutetium contents, on the other hand, are mainly composed of spherical particles. The Gd(1.9-x)LuxEu0.1O3 precursor powders were converted into crystalline lutetium gadolinium oxide after calcining at 800℃. The particle size of the Gd(1.9-x)LuxEu0.1O3 were 20nm～60nm. Transparent Gd0.9Lu1.0Eu0.1O3 and Lu1.9Eu0.1O3 ceramic scintillators were fabricated by vacuum sintering at 1700℃for 24h. The in-line transmittance of Gd0.9Lu1.0Eu0.1O3 and Lu1.9Eu0.1O3 transparent ceramics were 55.5% and 64.3% in the visible-light region, respectively. The as-sintered Gd(1.9-x)LuxEu0.103 ceramics show intense red luminescence at 612.5nm under 254nm UV excitation, corresponding to 5Do-7F2 transition of Eu3+ ion.The solid-state reaction method was utilized to produce LuAG:Ce polycrystalline ceramics. The high dispersity of the obtained power is mainly resulted from fine size of nano-Lu2O3 and nano-γ-Al2O3 powders used. The green bodies were pre-sintered at 1200℃and transparent LuAG:Ce ceramic scintillators were fabricated by vacuum sintering at 1700℃for 5h. The in-line transmittance of LuAG:Ce transparent ceramics were 57% in the visible-light region and 63.2% in the near infrared region, respectively. The in-line transmittance of LuAG and LuAG:Ce transparent ceramics sintered at 1700℃for 24h were 72% and 63.1% in the visible-light region,73.4% and 65.4% in the near infrared region, respectively. The photo luminescence spectra has the characteristic peaks at 512nm and 547nm duo to the splitting of the Ce3+ 4f ground state.
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