Synthesis of Yb²⁺ Long-Afterglow Phosphors in Strontium Aluminates via a Solid-Phase Reaction

抄録

Long-afterglow phosphors of strontium aluminates doped with Yb³⁺ and Dy³⁺ were prepared via a solid-phase reaction. The starting material powders (SrCO₃, Al(OH)₃, Eu₂O₃, and Dy₂O₃) were pulverized and mixed in a ball mill. The most emissive nominal composition was Sr_3.84Eu_0.08Dy_0.08Al₁₄O₂₅ sintered at 1450 °C in a reducing environment of 3 % H₂ in N₂ for 4 h. When the mixing and sintering cycle was repeated three times, the green emission intensity increased 28 times in comparison with that of the initial cycle. However, the emission intensity further increased to 120 times the initial upon addition of H₃BO₃ as a flux. The increase in the emission intensity is related to an increase in the presence of Sr₄Al₁₄O₂₅ and Sr₃Al₃₂O₅₁ phases. These crystalline phases doped with Yb²⁺ and Dy³⁺ are the most probable emission centers of the afterglow.