Different contents of SrAl 2 O 4 :Eu,Dy, one of the long afterglow phosphorescent materials with high brightness, were melt-mixed with low-density polyethylene (LDPE) and Polymethyl methacrylate (PMMA) polymers, respectively. The morphology and composition of the samples were observed by means of a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), and transmission electron microscope (TEM). Sharp and broad X-ray diffraction (XRD) peaks were observed for the LDPE and the PMMA composites respectively, reflecting configuration characteristics similar to those of the respective pure polymers. TEM micrographs show a transition from nanosized particles to cluster formation with increase in phosphor concentration. The green long-lasting phosphorescence of the composites was observed in the dark after removal of the excitation light. Photoluminescence (PL) was observed in the composites of both polymers for phosphor volume concentrations above 1.0% for PMMA and above 0.5% for LDPE. For each of these samples, a broad PL peak at about 505 nm wavelength was observed after excitation at 350 nm with a xenon lamp. For the LDPE composites, the DSC results show that the presence of the phosphor in the polymer has no major influence on either the melting temperature or enthalpy values of the polymer.
Europium and dysprosium codoped strontium aluminate green phosphor was synthesized by combustion method using urea as reducer and fuel. The morphology, particle size, and structure of the products were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy, while the characteristic luminescence properties were investigated using excitation and emission spectra. Polymer-phosphor composites were made and thermally characterized by means of differential scanning calorimetry and thermogravimetric analysis. Phosphor nanocrystallites with high brightness were obtained without significantly changing the structure of the aluminate host. The average crystallite sizes, calculated from the Scherrer equation ranged between 34 6 7 and 43 6 7 nm. Emissions arising from transitions between the 5d and 4f orbital gaps of Eu 2þ are manifested in the broadband excitation and emission spectra with major peaks at 360 and 515 nm, respectively. The decay curves and half-life times show a clear trend in the influence of the phosphor in the improvement of the initial brightness and the afterglow times, which are ascribed to the presence of shallow and deep traps. Thermal results indicate that the phosphor nanoparticles acted as nucleating agents and improved the overall crystallinity in the LDPE/phosphor system. POLYM. COMPOS., 32:219-226, 2011. ª
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