Influence of pH on the formation and luminescence properties of the sol–gel derived SrAl 2 O 4 : Eu 2+,Dy 3+ phosphors

Europium and dysprosium ions codoped strontium aluminates (SrAl₂O₄: Eu²⁺, Dy³⁺) phosphors were prepared via a pH controlled sol–gel process. Monophasic SrAl₂O₄: Eu²⁺, Dy³⁺ phosphors were obtained after calcination at 1250°C. An established model based on theoretical calculations was adopted to evaluate the concentrations of strontium, aluminium, europium and dysprosium species in citric solution under different pH conditions. With increasing pH of the solutions, the extent of chelation of metal ions with citrate ligands was increased. The emission and excitation intensities both increased with a rise in pH of the prepared solution. Two broad excitation peaks peaking at 254 and 324 nm were observed in ultraviolet region. The ultraviolet excited SrAl₂O₄: Eu²⁺, Dy³⁺ phosphors yielded a broad band with an emission peak centred at 524 nm. The sol–gel derived SrAl₂O₄: Eu²⁺, Dy³⁺ phosphor is considered a promising material for application in white light emitting diodes.