Radiative Transition Probabilities in Tb³⁺ and Fluorescence Colors Producible by Tb³⁺-Activated Phosphors

For the purpose of evaluating the electric dipole and the magnetic dipole transition prababilities in Tb 3+ , the reduced matrix elements for 5 D 4 → 7 F J and 5 D 3 → 7 F J have been calculated. From the results, fluorescence colors producible by Tb 3+ -activated phosphors have been predicted: The best green colors with short persistence have the chromaticity coordinates around x =0.321, and y =0.651. For this purpose, Tb 3+ ions should be embedded in lattice sites without inversion symmetry. The nonradiative transition probabilities for 5 D 3 → 5 D 4 due to multipolar interactions have been evaluated. When the Tb concentration is higher than several per cent, the quadrupole-dipole interaction between the Tb 3+ ions in the metastable state 5 D 3 and those in the ground state 7 F 6 is predominantly responsible for the nonradiative 5 D 3 → 5 D 4 relaxation.