The combinatorial approach for the discovery of new scintillating materials has been investigated using the wet-chemical (sol-gel) synthesis methods. Known scintillating compounds Lu 2 SiO 5 (LSO) and (LuAl)O 3 (LAO) and solid solutions in the systems of Lu 2 O 3 -Y 2 O 3 -SiO 2 (CeO 2doped) (LYSO) and Lu 2 O 3 -Y 2 O 3 -Al 2 O 3 (CeO 2 -doped) (LYAO) were synthesized from sol-gel precursors. Sol-gel precursors were formulated from alkoxides and nitrates and acetates of the cations. Sol-gel

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... tion precursors were formulated for the printing of microdot arrays of different compositions in the above oxide systems. Microdot arrays were successfully printed on C-cut and R-cut sapphire substrates using Biodot printer at Los Alamos National Laboratory (LANL). The microdot arrays were adherent and stable after heat-treating at 1665 o C and had an average thickness of around 2µm. X-ray fluorescence elemental mapping showed the arrays to be of the correct chemical composition. Sintered microdots were found to be highly crystalline by microscopic observation and x-ray diffraction. Scintillation was not clearly detectable by visual observation under UV illumination and by video observation under the scanning electron beam of an SEM. The microdots were either poorly scintillating or not scintillating under the present synthesis and testing conditions. Further improvements in the synthesis and processing of the microdot arrays as well as extensive scintillation testing are needed. EXPERIMENTAL Experimental work involved two parts. First, the well known scintillating compounds, Ce-doped Lu 2 SiO 5 (or LSO) and Ce-doped Lu 3 Al 5 O 12 (LAO) [usually referred to as (LuAl)O 3 (LAO)], were synthesized by sol-gel method. Second, a combinatorial approach was applied to print by the same sol-gel method microdot arrays of the systems Lu 2 O 3 -Y 2 O 3 -SiO 2 (CeO 2 -doped) (CeO 2 -doped) (LYAO). Formation of the crystalline phases was confirmed by x-ray diffraction (XRD) and thickness of the heat treated dots was measured using surface profilometry (Alpha Step). The arrays were examined visually using an optical microscope at magnifications of 75 and 150X. Materials Chemicals: Lutetium(III) nitrate hydrate: Lu(NO 3 ) 3 . xH 2 O, FW 360.98 (Aldrich #436429-5G). Lutetium(III) acetate hydrate, 99.9% : (CH 3 CO 2 ) 3 Lu.xH 2 O, FW 352.10 (Aldrich # 325783-5G). Cerium (III) acetate hydrate, 99.9%: (CH 3 CO 2 ) 3 Ce.xH 2 O (x=1-3) FW: 317.26 for x=0; FW = 353.26 for x=2 (Aldrich # 367753-50G). Aluminum nitrate nonahydrate, 99.997% : Al(NO 3 ) 3 .9H 2 O, FW 375.13 (Aldrich # 229415-10G). Tetraethylorthosilicate (TEOS), 98%: Si(OC 2 H 5 ) 4 , FW 208.33 (Aldrich # 131903-500ML). Yttrium (III) acetate tetrahydrate, 99.9% (REO): Y(OOCCH 3 ) 3 .4H 2 O, FW 338.09 (Alfa-Aesar Stock # 14565). Substrates: Arrays were deposited onto optically polished fused silica and sapphire circles. The characteristics of the sapphire substrates were as follows: