| 초록 |
$BaMoO_4:Tb^{3+}$ phosphor powders were synthesized with different concentrations of $Tb^{3+}$ ions using the solid-state reaction method. XRD patterns showed that all the phosphors, irrespective of the concentration of $Tb^{3+}$ ions, had tetragonal systems with two main (112) and (004) diffraction peaks. The excitation spectra of the $Tb^{3+}$ -doped $BaMoO_4$ phosphors consisted of an intense broad band centered at 290 nm in the range of 230-330 nm and two weak bands. The former broad band corresponded to the $4f^8{ rightarrow}4f^75d^1$ transition of $Tb^{3+}$ ions; the latter two weak bands were ascribed to the $^7F_2{ rightarrow}^5D_3$ (471 nm) and $^7F_6{ rightarrow}^5D_4$ (492 nm) transitions of $Tb^{3+}$ . The main emission band, when excited at 290 nm, showed a strong green band at 550 nm arising from the $^5D_4{ rightarrow}^7F_5$ transition of $Tb^{3+}$ ions. As the concentration of $Tb^{3+}$ increased from 1 to 10 mol%, the intensities of all the emission lines gradually increased, approached maxima at 10 mol% of $Tb^{3+}$ ions, and then showed a decreasing tendency with further increase in the $Tb^{3+}$ ions due to the concentration quenching effect. The critical distance between neighboring $Tb^{3+}$ ions for concentration quenching was calculated and found to be $12.3{ AA}$ , which indicates that dipole-dipole interaction was the main mechanism for the concentration quenching of the $^5D_4{ rightarrow}^7F_5$ transition of $Tb^{3+}$ in the $BaMoO_4:Tb^{3+}$ phosphors. |
