A new orange-yellow-emitting Sr9Mg(1.5)(PO4)7:Eu(2+) phosphor was prepared via high-temperature solid-state reaction. The structure and optical properties of it were studied systematically. Sr9Mg(1.5)(PO4)7:Eu(2+) can be well-excited by 460 nm blue InGaN chips and exhibit a wide emission band covering from 470 to 850 nm with two main peaks centered at 523 and 620 nm, respectively, which originate from 5d-4f dipole-allowed transitions of Eu(2+) in different crystallographic sites. The sites attribution, concentration quenching, fluorescence decay analysis, and temperature-dependent luminescence properties were investigated in detail. Furthermore, a warm white LED device was fabricated by combining a 460 nm blue InGaN chip with the optimized orange-yellow-emitting Sr9Mg(1.5)(PO4)7:Eu(2+). The color coordinate, correlated color temperature and color rendering index of the fabricated LED device were (0.393, 0.352), 3437 K, and 86.07, respectively. Sr9Mg(1.5)(PO4)7:Eu(2+) has great potential to serve as an attractive candidate in the application of blue light-excited warm white LEDs.
In this article we synthesized a series of phosphors KMgGeO:Bi with high brightness for white light-emitting diodes (WLEDs) conversion and investigated their crystal structures and luminescence properties using powder X-ray diffraction, diffuse reflectance spectra, X-ray photoelectron spectroscopy, photoluminescence spectra, and absolute quantum efficiency. KMgGeO:Bi phosphor exhibits intense absorption in near-UV area and presents a broad asymmetric emission band with the main peak located at 614 nm, which was ascribed to the P → S transition of Bi. The absolute quantum efficiency of the KMgGeO:0.01Bi phosphor was measured to be 66.6%. Also, this orange emission with color chromaticity coordinates of (0.4989, 0.4400) has an excellent resistance to thermal quenching: its integrated intensity at 393 K still maintained ∼85% of the one at room temperature. The WLEDs devices with R = 93.8 were fabricated by employing KMgGeO:0.01Bi as an orange phosphor, which contains abundant red light component in its emission spectrum. The excellent luminescent performance of KMgGeO:0.01Bi suggests that it is a promising orange-emitting phosphor for near-ultraviolet WLEDs.
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