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

Highlights: • The emission intensity of Sr_4.72Lu_0.2(PO₄)₃Cl: Eu²⁺ is 1.97 times of Sr_4.95(PO₄)₃Cl: Eu²⁺. • The emission intensity of Sr_4.72Lu_0.2(PO₄)₃Cl: Eu²⁺ phosphor maintains 95% of the initial intensity at 150 ℃. • A WLED device with an excellent CRI (Ra = 95.1) and low CCT (3775 K) is obtained. -- Abstract: Blue phosphor Sr_5−x-yR_y(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 Sr_5−x-yR_y(PO₄)₃Cl:xEu²⁺ phosphors show better luminescence intensity and thermal stability. The emission intensity of Sr_4.72Lu_0.2(PO₄)₃Cl:0.08Eu²⁺ is 1.97 times of Sr_4.95(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 Sr_4.72R_0.2(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 Sr_4.72Lu_0.2(PO₄)₃Cl:0.08Eu²⁺ maintains 95% while BAM:Eu²⁺ is only 88% of the initial intensity at 150 °C. By combining Sr_4.72Lu_0.2(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.