Synthesis, characterization and photoluminescence properties of (Gd1−x,Eux)2O2SO4 sub-microphosphors by homogeneous precipitation method

(Gd1−x,Eux)2O2SO4 sub-microphosphors were synthesized by homogeneous precipitation method from commercially available Gd2O3, Eu2O3, H2SO4 and (NH2)2CO (urea) starting materials. Fourier transform infrared spectra show that the precursors with different molar ratios of (NH2)2CO to Gd2(SO4)3 (the m value) are mostly composed of gadolinium hydroxyl, carbonate and sulfate groups with some crystal water. X-ray diffraction indicated that the precursor (m = 5) can be transformed into pure Gd2O2SO4 phase after heat treated at 900 °C for 2 h in air. Field emission scanning electron microscope micrographs illustrate that the Gd2O2SO4 phosphor particles (m = 5) are quasi-spherical in shape and well dispersed, with a mean particle size of about 300-500 nm. Photoluminescence spectroscopy reveals that the strongest emission peak for (Gd1−x,Eux)2O2SO4 sub-microphosphors is located at 618 nm under 270 nm light excitation, which corresponds to the 5D0 → 7F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions is 5 mol% and the concentration quenching mechanism is due to the electric dipole-dipole interaction. Decay study reveals that the 5D0 → 7F2 transition of Eu3+ ions fits with a mono exponential function.