(A) Study on the Eu- and Tb-Activated Phosphors in the System $MO-Gd_2O_3-Al_2O_3$ (M=Mg, Ca, Sr, Ba) by Combinatorial Chemistry

Abstract

The polymerized-complex combinatorial chemistry has been developed and applied to the synthesis and the screening of phosphor powders. This combinatorial chemistry method made it possible to characterize all the properties of an individual sample in the libraries in the same way as for a conventional individual powder sample. Thus, it was possible to use conventional UV/VUV spectroscopic techniques to measure all properties of a member samples in the libraries of materials. The Eu- or Tb-doped phosphors for plasma display panel (PDP) were investigated in the system of $MO-Gd_{2}O_{3}-Al_{2}O_{3}$ (M=Mg, Ca, Sr, Ba). As a result, the ternary material libraries of a triangle-type composition array were set up to seek the optimum composition for stabilizing the activator $Eu^{3+}$, $Eu^{2+}$ and $Tb^{3+}$, respectively. From the $Eu^{3+}$ material libraries of $MO-Gd_{2}O_{3}-Al_{2}O_{3}$ (M=Mg, Ca, Sr, Ba), $Gd_{2}O_{3}$:Eu, $M_{x}$ and/or $Al_{y}$ (M=Mg, Ca, Sr, Ba, 0<x<0.05, 0≤y<0.05 ) could be determined as the candidate phosphor for plasma display panel. From the $Eu^{2+}$ material libraries of $MO-Gd_{2}O_{3}-Al_{2}O_{3}$ (M=Mg, Ca, Sr, Ba), it was found that $CaAl_{2}O_{4}$, $4SrOㆍ7Al_{2}O_{3}$, $BaAl_{2}O_{4}ㆍGdAlO_{3}$ and $Ba_{0.75}Al_{11}O_{17.25}ㆍGdAlO_{3}$ had good luminescent properties. In case of the $Tb^{3+}$ ion in the system $MO-Gd_{2}O_{3}-A_{2}O_{3}$ (M=Mg, Ca, Sr, Ba), the efficient $Tb^{3+}$ phosphors appeared in various compositions. $Gd_{4}Al_{2}O_{9}ㆍGd_{2}O_{3}$, $Gd_{3}Al_{5}O_{12}$ with small $GdAlO_{3}$, and $CaAl_{12}O_{19}$ were observed as the candidate host lattice. In special, $Ca_{x}Gd_{0.95-x-y}Tb_{0.05}Al_{y}O_{δ}$ (0.25≤x≤0.35, 0.45<y<0.60 ) had good luminescence. Their samples were the admixture of $CaGdAl_{3}O_{7}$, $CaGdAlO_{4}$ and $GdAlO_{3}$ according to XRD analysis. In order to assess the exact value of the fraction of each compound, a quantitative estimation could be obtained using the Rietveld method with the F...