Synthesis and evaluation of photocatalytic properties of Na–TiO₂/Sr₄Al_l4O₂₅:Eu,Dy phosphor composites

Sub-micron Sr₄Al₁₄O₂₅:Eu,Dy phosphor particles were coated by a TiO₂-sol precipitation procedure at 80 °C for 3 h. The effects of Na/H₂O₂ additives on TiO₂ precipitation and stability of the composites over heat treatment conditions were evaluated. The distribution of TiO₂ nanoclusters on the sub-micron phosphor support changed from sparse to dense clusters with increasing Na additive. X-ray diffraction and Raman spectroscopy analyses revealed that the anatase and rutile phases dominated in the Na–TiO₂/phosphor nanocomposites at 300 °C. Heat treatment at 450 °C was detrimental to the stability of TiO₂ anatase phase. Ultraviolet and visible light were utilized for photocatalytic decomposition of methylene blue and toluene volatile organic components in the vicinity of the Na–TiO₂/phosphor composites. Optimum photocatalytic performances were obtained in TiO₂/phosphor composites with low concentration precipitation additives (1% Na and 0.23 vol% H₂O₂) heat-treated at 300 °C. Anatase phases and Na⁺ existence in TiO₂/Sr₄Al₁₄O₂₅:Eu,Dy phosphor composites improved the light sensitization and overall photocatalytic efficiencies.