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Abstract A series of Y 5 Si 3 O 12 N:Ce3+ single-doped and Ce3+/Tb3+ co–doped phosphors, as potential candidates for application in tri–chromatic white LEDs, were successfully synthesized by a high temperature solid state reaction method. The addition of Li 2 CO 3 flux (5 wt%) improved the purity of the resultant phosphors and increased their emission intensity. An intense, broad excitation band in the range of 200–400 nm with a peak at 358 nm was recorded, which suits the needs of UV LED chips. Under this excitation wavelength, intense blue emission, which peaked at 439 nm, was recorded in the Ce3+ single-doped phosphors, while two distinct luminescence bands were observed in the Ce3+/Tb3+ co–doped Y 5 Si 3 O 12 N phosphors: a blue one, which peaked at 439 nm and is ascribed to Ce3+ ions, and an efficient green one, which peaked at 549 nm and is assigned to 5D 4 →7F 5 transitions in Tb3+ ions. A high luminescence quantum yield, of 85%, was achieved. The experimental results illustrate that efficient energy transfer can take place from the sensitizer Ce3+ ions to the activator Tb3+ ions in the Ce3+/Tb3+ co–doped Y 5 Si 3 O 12 N phosphors, through predominantly dipole–dipole interactions. Highlights • Purity and emission intensity of the prepared phosphors are improved with flux addition. • Broad excitation band having maximum peak at 358 nm suits the needs of UV LED chips. • A high luminescence quantum yield, of 85%, was achieved. • The intensity of the emission at 150 °C is 80% of the intensity at room temperature. [ABSTRACT FROM AUTHOR]

Abstract Phosphors with tuning capabilities in their excitation and emission spectra are in high demand in the field of advanced optical technology. In this article, Eu2+ doped Ba 9 Lu 2 Si 6 O 24 (BLSO: Eu2+) phosphors, which emit an intense light hat can be tuned from dark blue (463 nm) to efficient green (514 nm), were produced, simply by increasing the Eu2+ concentration in the BLSO host lattice. This tuning capability suggests that there are multiple and distinguishable crystallographic sites in the host lattice of the BLSO phosphors. The Eu2+ activators exhibit preferable site distributions in the BLSO host lattice, depending on the Eu2+ concentration. This offers the possibility for engineering the appropriate site surroundings, available for the Eu2+ activators. The Ba 8.4 Eu 0.6 Lu 2 Si 6 O 24 phosphor displays a prominent yellowish-green emission under blue light (440 nm) excitation, compared to the dark blue emission of BLSO: 0.1Eu2+ phosphors. The green emission from the BLSO: xEu2+ phosphor is closely associated with the specific coordinating environment of the Eu2+ activator in various crystallographic Ba sites. However, concentration quenching phenomena results in intensity decrease, a problem which is then solved by introducing Sr2+. Graphical abstract Image 1 Highlights • Multiple and distinguishable crystallographic sites in the host lattice of the BLSO phosphors. • The Eu2+ activators exhibit preferable site distributions in the BLSO host lattice, depending on the Eu2+ concentration. • The Ba 8.4 Eu 0.6 Lu 2 Si 6 O 24 phosphor displays a prominent yellowish-green emission under blue light (440 nm) excitation. • Concentration quenching phenomena results in intensity decrease, a problem which is then solved by introducing Sr2+. [ABSTRACT FROM AUTHOR]

Red emitting Ba 2 Si (5-x) Al x N (8-x) O x :Eu 2+ phosphors were successfully produced by high-temperature solid state reaction method and their luminescence properties were experimentally measured. The analysis of the experimental results suggests that the partial substitution of Al-O for Si-N in the host lattice improves the photoluminescence properties and the thermal stability of the produced phosphors. The phosphors exhibited a broad red emission band between 500 and 750 nm. A red shift of emission peak from 588 to 624 nm was recorded with the increase of Al-O content, attributed to the enhancement of stokes shift. The excitation spectrum of the produced phosphors ranged between 200 and 600 nm, covering the UV and the blue region, and suggesting these materials as potentially suitable for use as conversion phosphors for white LED applications in the field of solid state lighting. [ABSTRACT FROM AUTHOR]