Novel Red-Emitting Microwave-Assisted-Sintered LiSrPO4: Eu3+ Phosphors for Application in Near-UV White Light-Emitting Diodes

Novel red-emitting LiSr1-x PO4:xEu(3+) phosphors with various concentrations (x = 0.03, 0.05, 0.07, 0.1) of Eu3+ ions were synthesized by microwave-assisted sintering at 1200A degrees C for 3 h in air. The microstructural and luminescent characteristics of the LiSrPO4:Eu3+ phosphors were investigated and are discussed here. x-Ray diffraction (XRD) results showed that the prepared LiSr1-x PO4:xEu(3+) phosphors presented an impurity phase of Eu2O3 when the Eu3+ ions exceeded x = 0.05. Photoluminescence (PL) results showed a series of emission states D-5(0) -> F-7(0), D-5(0) -> F-7(1), D-5(0) -> F-7(2), D-5(0) -> F-7(3), and D-5(0) -> F-7(4) (corresponding to the typical 4f -> 4f intraconfiguration forbidden transitions of Eu3+) with a major emission peak at around 617 nm. The optimum concentration of Eu3+ for LiSr1-x PO4:xEu(3+) prepared by microwave-assisted sintering was found to be 0.05. The lifetime values of LiSr1-x PO4:xEu(3+) phosphors with doping concentrations of Eu3+ ions of 0.03, 0.05, 0.07, and 0.1 were found to be 3.32 ms, 3.30 ms, 2.84 ms, and 2.60 ms, respectively. Moreover, the chromaticity values (x, y) of all of the LiSr1-x PO4:xEu(3+) phosphors were located in the red region (0.65, 0.34).