Structural and optical properties of SrAl₂O₄: Eu²⁺/Dy³⁺ phosphors synthesized by flame spray pyrolysis technique

In this study Sr_0.985Al₂O₄:0.005Eu²⁺/0.01Dy³⁺ luminescent materials with long afterglow and high intensity were synthesized by flame spray pyrolysis (FSP) method for the first time. Precursor solution was divided into two separate part. One of the parts was used FSP process, the other one was dried to simulate sol-gel process. Thermal properties and organic content of FSP derived particles and dried gel were compared using DTA-TG and FTIR devices. FSP derived particles were sintered in argon medium at 1200 ^oC. Phase and elemental analysis of the final phosphors were carried out by X-Ray Diffraction (XRD) and X-Ray Photo electron Spectroscopy (XPS) measurements. Scanning electron microscopy (SEM) images were obtained to observe particle morphology. Optical properties of phosphor were determined by Photoluminescence (PL), thermoluminescence (TL) and radioluminescence (RL) measurements. The emission spectra of Sr_0.985Al₂O₄:0.005Eu²⁺/0.01Dy³⁺ were composed by a green band at 525 nm at room temperature when it was excited by 350 nm light, assigned to anomalous luminescence originated by Eu²⁺ and Dy³⁺ in the host lattice. There were estimated peaks at around 90, 130, 170 and 200 ^oC under the main glow curve in the sample irradiated by X-ray and He-Ne laser (λ_exc = 632 nm). RL spectrum of Sr_0.985Al₂O₄:0.005Eu²⁺/0.01Dy³⁺ powders have four distinct emission peaks at around 527 nm, 576 nm, 667 nm, 753;nm and a comparatively weak emission band at about 846 nm.