A novel tunable blue-green-emitting CaGdGaAl2O7:Ce(3+),Tb(3+) phosphor via energy transfer for UV-excited white LEDs.

CaGdGaAl2O7 and CaGdGaAl2O7: Ce3+, Tb3+ have been synthesized by a traditional solid state reaction for the first time. The Rietveld refinement confirmed that CaGdGaAl2O7 has a tetragonal crystal system with the space group P (4) over bar 21m. The photoluminescence properties show that the obtained phosphors can be efficiently excited in the range from 330 to 400 nm, which matches perfectly with commercial UV LED chips. A tunable blue-green emitting CaGdGaAl2O7: Ce3+, Tb3+ phosphor has been obtained, by codoping Ce3+ and Tb3+ ions into the host and varying their relative ratios, and may be a good candidate for blue-green components in UV white LEDs. The luminescence properties and lifetimes reveal an efficient energy transfer from the Ce3+ to Tb3+ ions. The energy transfer is demonstrated to be a dipole-quadrupole mechanism, and the critical distance for Ce3+ to Tb3+ calculated by the concentration quenching is 12.25 angstrom.