Preparation and characterization of SiO₂-coated Sr₄A1₁₄O₂₅:Eu²⁺, Dy³⁺/light conversion agent yellow phosphor

The SiO₂-coated Sr₄A1₁₄O₂₅:Eu²⁺, Dy³⁺/light conversion agent yellow phosphor was prepared by the sol–gel method in alcohol/water system. The morphology, photochromic properties and water tolerance of the samples were analyzed and characterized by using XRD, SEM, FTIR, fluorescence spectrophotometer, spectroradiometer and pH meter. The results reveal that the silica and light conversion agent were successfully coated on the surface of Sr₄A1₁₄O₂₅:Eu²⁺, Dy³⁺. The emission peak shifted from 493 nm (Sr₄A1₁₄O₂₅:Eu²⁺, Dy³⁺) to 606 nm due to the cladding of the light conversion agent (LCA). But with the addition of silica, the property of light conversion agent was influenced by the hydrogen bonds and the electrostatic interactions between silica and light conversion agent. That caused the excitation energy of the light conversion agent risen, and the emission peak have a blue shift from 606 nm (Sr₄A1₁₄O₂₅:Eu²⁺, Dy³⁺/LCA) to 586 nm. Therefore, the composite phosphor was obtained that appeared yellow fluorescence while pink in the daylight. It is also important that the composite yellow phosphors have good water tolerance attributed to the coating of silica.