Synthesis and characterization of Sr₃Al₂O₆:Eu²⁺, Dy³⁺ phosphors prepared by sol--gel--combustion processing

A type of red luminescent Sr₃Al₂O₊:Eu²⁺, Dy³⁺ phosphor powder is synthesised by sol--gel--combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol--gel, it is found that it is necessary to reduce the amount of NO₃^- by dropping ethanol into the solution for forming a stable and homogeneous sol--gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr₃Al₂O₆:Eu²⁺, Dy³⁺. The results reveal that the Sr₃Al₂O₆ crystallises completely when the combustion ash is sintered at 1250 ℃. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618~nm under the excitation of 472 nm. The afterglow of (Sr_0.097Eu_0.03Dy_0.03)₃Al₂O₆ phosphors sintered at 1250 ℃ lasts for over 1000 s when the excited source is cut off.