Significantly enhanced photoluminescence and thermal stability of La 3 Si 8 N 11 O 4 :Ce 3+ ,Tb 3+ via the Ce 3+ → Tb 3+ energy transfer: a blue-green phosphor for ultraviolet LEDs.

A series of Ce 3+ -, Tb 3+ - and Ce 3+ /Tb 3+ -doped La 3 Si 8 N 11 O 4 phosphors were synthesized by gas-pressure sintering (GPS). The energy transfer between Ce 3+ and Tb 3+ occurred in the co-doped samples, leading to a tunable emission color from blue to green under the 360 nm excitation. The energy transfer mechanism was controlled by the dipole-dipole interaction. The Ce 3+ /Tb 3+ co-doped sample had an external quantum efficiency of 46.7%, about 5.6 times higher than the Tb-doped La 3 Si 8 N 11 O 4 phosphor (8.3%). The thermal quenching of the Tb 3+ emission in La 3 Si 8 N 11 O 4 :Tb,Ce was greatly reduced from 74 to 30% at 250 °C, owing to the energy transfer from Ce 3+ to Tb 3+ . The blue-green La 3 Si 8 N 11 O 4 :0.01Ce,0.05Tb phosphor was testified to fabricate a warm white LED that showed a high color rendering index of 90.2 and a correlated color temperature of 3570 K. The results suggested that the co-doped La 3 Si 8 N 11 O 4 :Ce,Tb phosphor could be a potential blue-green down-conversion luminescent material for use in UV-LED pumped wLEDs.