Synthesis process of BaMgAl₁₀O₁₇:Eu²⁺ from sol-gel-derived Eu²⁺-activated fluoride precursors without H ₂ annealing treatments

Barium magnesium aluminate, BaMgAl₁₀O₁₇, was synthesized by a solid-state reaction between Al₂O₃ and sol-gel-derived BaMgF₄ 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 BaMgF₄ was also prepared and characterized to examine its suitability as a precursor for synthesizing BaMgAl₁₀O₁₇:Eu ²⁺ blue phosphors. It was demonstrated that Eu³⁺, which was used in the acetate form as a starting material, was reduced to Eu ²⁺ in the sol-gel processing of BaMgF₄, as indicated by a broad blue emission due to an allowed d-f transition at 420 nm with an ultraviolet excitation at 290 nm. BaMgAl₁₀O₁₇:Eu ²⁺, which showed efficient blue emissions at 450 nm with an ultraviolet excitation at 254 nm, was successfully prepared by heating a mixture of Al₂O₃ and Eu-doped BaMgF₄ at 1300°C without any special reducing treatment.