Direct synthesis of BaAl₂S₄:Eu²⁺ blue emission phosphor by one-step sulfurization of highly homogeneous oxide precursor prepared via a solution-based method

A study was conducted to analyze the synthesis of BaAl₂S ₄:Eu phosphor material employing a solution method. The study showed that sulfurization does occur, though it is not complete, and an oxysulfide phase forms as an intermediate compound. Additional annealing in the Ar/CS ₂ glass flow was necessary, while BaAl₂S₄:Eu was found to be the main phase after the second annealing, and the third annealing yields an almost single phase cubic BaAl₂S₄:Eu. The results of the study show substantially better homogeneity of the material prepared by the solution method compared to BaAl₂S₄ synthesized by the solid state reaction. The study also found that the synthesis route is insensitive to ambient humidity because it does not have to deal with unstable sulfides such as BaS and Al₂S₃ used in the usual ceramic method.