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Barium magnesium aluminate, BaMgAl 10 O 17 , was synthesized by a solid-state reaction between Al 2 O 3 and sol-gel-derived BaMgF 4 precursors. The reaction temperature necessary for producing a single-phase material was reduced to 1300°C because of the higher reactivity and lower melting point of the fluoride precursors. Eu-doped BaMgF 4 was also prepared and characterized to examine its suitability as a precursor for synthesizing BaMgAl 10 O 17 :Eu 2ϩ blue phosphors. It was demonstrated that Eu 3ϩ , which was used in the acetate form as a starting material, was reduced to Eu 2ϩ in the sol-gel processing of BaMgF 4 , as indicated by a broad blue emission due to an allowed d-f transition at 420 nm with an ultraviolet excitation at 290 nm. BaMgAl 10 O 17 :Eu 2ϩ , which showed efficient blue emissions at 450 nm with an ultraviolet excitation at 254 nm, was successfully prepared by heating a mixture of Al 2 O 3 and Eu-doped BaMgF 4 at 1300°C without any special reducing treatment.

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2002 luminescence, fluorescence luminescence, fluorescence (solids and liquids) D 6540 -011Sol-Gel Processing of BaMgF 4 -Eu 2+ Thin Films and Their Violet Luminescence.-Thin films of the title compound are prepared by a sol-gel method from isopropanol solutions of Ba(OAc) 2 , Mg(OAc) 2 ·4H 2 O, Eu(OAc) 3 ·4H 2 O, CF 3 COOH, and H 2 O (20 • C, 2 h, followed by spin coating and heating at 500-700 • C for 10 min). The reduction of Eu 3+ to Eu 2+ in the heat-treated films is evidenced by the strong, broadband 4f-5d excitation at 290 nm and emission at 420 nm in photoluminescence measurements. The intensity of the violet luminescence of Eu 2+ depends on the heating temperature, heating time, and Eu concentration. The strongest violet emission is observed for the BaMgF 4 :Eu (15 mol%) thin film heated at 650 • C for 10 min.