Energy transfer and thermal stability of novel green-emitting Ca3Y(PO4)3:Ce3+, Tb3+ phosphors for white LEDs

A novel thermally high-stable and high-efficiency green-emitting Ce3+/Tb3+ co-doped Ca3Y(PO4)3 phosphor has been successfully synthesized via a conventional solid-state reaction. The energy transfer and thermal quenching of Ca3Y(PO4)3:Ce3+, Tb3+ samples were investigated for the first time. The emission spectra of as-prepared samples presented a blue emission band deriving from the 5d-4f transition of Ce3+ and green emission peaks stemmed from 5D4-7FJ (J = 6, 5, 4, 3) of Tb3+ upon 325 nm excitation. By adjusting Tb3+ concentration, the chromaticity coordinates of as-prepared samples could be tuned from (0.165, 0.028) to (0.301, 0.529) because of the energy transfer of Ce3+→Tb3+ ions. It was demonstrated that the energy transfer mechanism from Ce3+ to Tb3+ ions in Ca3Y(PO4)3 host is the electric dipole-dipole interaction by the energy level diagram and the spectral overlap between the emission spectrum of the donor and the excitation spectrum of the acceptor. The energy transfer efficiency from Ce3+ to Tb3+ ions in Ca3Y(PO4)3 was up to 81%. Beyond that, it affirmed that the emission intensity at 423 K was about 82% of that measured at room temperature (298 K) according to the temperature-dependent emission spectra. Basing on the above analyses shows that the as-synthesized green-emitting Ce3+/Tb3+ co-doped Ca3Y(PO4)3 phosphors with high energy transfer efficiency and excellent thermal stability could be used in phosphor-converted white light-emitting-diodes (LEDs).