CONCENTRATION QUENCHING OF TB3+ LUMINESCENCE IN LAOBR AND GD2O2S PHOSPHORS

The concentration quenching of trivalent terbium 5D3,4 → 7FJ emissions from UV-excited (La, Tb) OBr and (Gd, Tb)2O2S phosphors was studied. The activation concentration x was varied from 5·10-5 to 0.2 for (La1-xTbx) OBr and from 10-3 to 0.1 for (Gd1-xTbx)2O2S. 5D3 → 7FJ emissions (blue) were observed to quench first and the Tb3+ concentration giving rise to maximum intensity was 0.003 in (La, Tb) OBr and between 0.005 and 0.01 in (Gd, Tb)2O2S. The optimum concentration for 5D4 → 7FJ (green) emissions was 0.05 in (La, Tb) OBr and 0.03 in (Gd, Tb)2O2S. Dipole-dipole and dipole-quadrupole interactions are possible mechanisms for the quenching of emissions from the 5D3 and 5D4 levels. A method for determining the Tb3+ concentration in these phosphors, based on the intensity ratios of the 5D3 → 7FJ and 5D4 → 7FJ transitions, is also presented. © 1979.