Combustion Synthesis and Spectra Characteristic of Gd 2 O 2 S:Tb 3+ and La 2 O 2 S:Eu 3+ X-ray Phosphors
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X-ray phosphors of Gd2O2S:Tb3+ and La2O2S:Eu3+ were synthesized by combustion reactions. The samples were characterized by x-ray diffraction (XRD), scanning electronic microscope (SEM), photoluminescence (PL), and x-ray excited luminescence (XEL) spectra. XRD results revealed pure oxy-sulfide phases when the sintering temperatures were no more than 500 °C, and the mean particle sizes were about 20 nm. While the sintering temperatures became higher, oxy-sulfate phases were present. SEM results illustrated a loose, porous agglomeration and a continuous three-dimensional network structure; PL spectra showed the characteristic emission of rare-earth activation ions. To our satisfaction, the PL intensities were nearly the same as some commercial x-ray phosphors. XEL spectra revealed the same characteristic emission, although their luminescence principles were different from those of the PL spectra. In addition, because absorption coefficients of these samples for x-ray and doped concentrations doped of activation ions were different, their light emission intensities and efficiencies also varied.
I. INTRODUCTION
As is well known, CaWO4 can greatly enhance the light output from x-ray to visible light; thus, the type of phosphor was solely used for 75 years. Since the 1970s, the phosphors of rare earth have been applied widely, which have larger densities, stronger x-ray absorbance abilities, and higher transition efficiency from x-ray to visible light. X-ray phosphors are commercially produced by solid-state reactions; this kind of conventional phosphor synthesis techniques involves several timeconsuming multiple process steps1,2 and the need for high temperatures. Uniform, spherical phosphor powders favored in the screening process are desirable for highquality display devices. However, it is difficult to control the morphology of phosphor powders using hightemperature solid-state reactions. To achieve highresolution displays, phosphor powders with a small particle size (
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