Turning on the luminescence of Sr5(PO4)3Cl: Eu2+ by doping of La, Gd and Lu ions for full-spectrum lighting application

Abstract

Blue phosphor Sr5−x-yRy(PO4)3Cl:xEu2+ (R = La, Gd, Lu) was prepared via solid-state reaction process, in which R3+ replaces part of Sr2+ ions in the matrix to benefit Eu2+ luminescence. The change of Eu2+/Eu3+ values were studied by XPS, and the results shown that the incorporation of R3+ in the matrix resulted in the values increase of Eu2+/Eu3+. And substitute R3+ non-equivalently for Sr2+, the modified Sr5−x-yRy(PO4)3Cl:xEu2+ phosphors show better luminescence intensity and thermal stability. The emission intensity of Sr4.72Lu0.2(PO4)3Cl:0.08Eu2+ is 1.97 times of Sr4.95(PO4)3Cl:0.05Eu2+. Moreover, the thermal quenching of Eu2+ photoluminescence could be reduced. Compared to the commercial BAM:Eu2+ phosphor, the stabilities of all Sr4.72R0.2(PO4)3Cl:0.08Eu2+(R=La3+, Gd3+ and Lu3+) phosphors are better than that of BAM:Eu2+ at the temperatures below 100 °C. The luminescent intensity of Sr4.72Lu0.2(PO4)3Cl:0.08Eu2+ maintains 95% while BAM:Eu2+ is only 88% of the initial intensity at 150 °C. By combining Sr4.72Lu0.2(PO4)3Cl:0.08Eu2+, Y3(Al,Ga)5O12:Ce3+ and CaAlSiN3:Eu2+ with 400 nm near-ultraviolet LED chip, a white-light-emitting diode was obtained. The fabricated WLED device with CIE color coordinates x = 0.3896, y = 0.3788, low CCT (3775 K) and high Ra (95.1), has enormous potential application in full-spectrum lighting field.