Synthesis, structure and green luminescence evolution of apatite-type Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5:Eu2+,Tb3+ phosphors

Eu2+-Tb3+ co-doped Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5 (SYPSO) phosphors with apatite structure have been synthesized via a high temperature solid-state reaction and their luminescence properties have been investigated in detail. The two kinds of cations׳ sites and complex phosphate-silicate anions׳ structural character of SYPSO host have been studied. The SYPSO:Eu2+,Tb3+ phosphors show a broad absorption band ranging from 250 to 420 nm, which is well matched with the emission of near ultraviolet (UV) chips, and it exhibited two dominating bands peaked at 502 and 543 nm upon 365 nm excitation. The emission color of SYPSO:0.05Eu2+,yTb3+ shows a controlled luminescence evolution of the color hue in the green area owing to the Eu2+-Tb3+ energy transfer (ET) process, and their chromaticity coordinates (x, y) can be varied from (0.2723, 0.3766) to (0.2812, 0.4537). The ET efficiency as well as the critical distance is also estimated. The quantum efficiency and thermal quenching properties have also been studied in this paper in order to demonstrate its potential application for white light-emitting diodes (w-LEDs) phosphors.