Study on Fabrication of Intense Fluorescent Oxides doped with Rare Earths

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Fluorescent Oxides doped with rare earths such as Tm^<3+>, Tb^<3+> and Eu^<3+> have attracted much attention because of their blue, green and red luminescence. However, an enriched quantity of rare earths frequently leads to a quenching phenomenon in luminescence owing to the energy transfer between rare earth ions i. e. concentration quenching. It is important to elucidate the quenching mechanism in oxides in order to realize intense fluorescence. In the present study, the luminescence properties of Tm^<3+>, Tb^<3+> and Eu^<3+> in (La_<1-X>R_X) Ta_7O_<19> (R=Tm, Tb, Eu) solid solutions were examined systematically. X-ray diffraction patterns of the solid solutions indicated wat the crystal structure consisted of a network of (La^<3+>_<1-X>R^<3+>_X, Ta^<5+>)-O^<2-> polyhedra interstratified with a double layr of Ta^<5+> -O^<2-> polyhedra. According to the emission spectra, the most intense emissions were found near 460nm and X=0.14 in (La_<1-X>Tb_X) Ta_7 O_<19>, near 547nm and X=0.8 IN (La_<1-X> Tb_X) Ta_7O_<19>, near 610nm and X=1.0 in (La_<1-X>Eu_X)Ta_7O_<19>. As a results, a low dimensional arrangement of Tm^<3+>, Tb^<3+> or Eu^<3+> was much more preferable for getting intense emission, because it reduced the energy migration between rare earth ions in (La_<1-X>R_X) Ta_7O_<19> solid solutions.