Combustion Synthesis and Spectra Characteristic of Gd₂O₂S:Tb³⁺ and La₂O₂S:Eu³⁺ X-ray Phosphors

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.