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Superior thermal quenching and degradation of phosphors are required for long lifetime lighting devices, such as light-emitting diodes, which can be realized through composition modification. Here, Al-N bonds in AlON: Eu 2+ phosphors are substituted by higher bond order of Si-C. Photoluminescence (PL) results show thermal quenching (at 150 °C) and thermal degradation (after 600 °C treatment in air) are improved by 5% and 8% with a small decrease of PL intensity in 5% SiC doped AlON: Eu 2+ phosphor. To explain these observations, first-principles computational study was performed to understand the Si and C configuration in AlON:Eu 2+ . The calculations reveal that Si and C elements are not randomly distributed in AlON lattice. It was found that Si prefers occupying tetrahedral sites (Td-Si) and the insertion of C in Td-Si is always energetically favorable, which results in the formation of SiC 4 and SiNC 3 clusters. Thus, the Al-N substitution by Si-C induces a stronger local structure, which accounts for the emission redshift and better thermal stability. [ABSTRACT FROM AUTHOR]

A series of quaternary nitride solid solutions with a general formula of Sr1-xCaxLiAl3N4:0.5%Eu2+ was synthesized by a solid-state reaction method. The experimental results showed that a proper amount of Ca-doping can improve the crystallinity and the photoluminescence properties of the produced phosphors. Rietveld refinement showed that the volume of the unit cell shrank with the increase of Ca substitution for Sr, which resulted in a red shift of the emission spectra from 654 to 665 nm under blue excitation at 475 nm. Rietveld refinement and CASTPE calculations suggested that Ca2+ ions prefer to occupy the smaller Sr(I) sites in the crystal lattice, which increases the amount of Eu2+ ions in Sr(II) sites and enables the tuning of the chromaticity coordinates of the obtained phosphors. The thermal stability of the produced phosphors is better than that of commercial Sr2Si5N8:Eu2+ phosphor. The experimental results qualify the solid-solution Sr1-xCaxLiAl3N4:0.5%Eu2+ for consideration as a potential candidate for application in white LEDs. [ABSTRACT FROM AUTHOR]

A novel Al 10 O 3 N 8 :Eu 2+ phosphor was prepared successfully by a mechanochemical activation route. With the help of high-energy ball milling, the starting materials were mostly transformed into an amorphous phase, which significantly promotes the synthesis of Al 10 O 3 N 8 phase at a relatively moderate reaction condition. Al 10 O 3 N 8 :Eu 2+ phosphor showed a broad blue emission band under ultraviolet-light excitation and small thermal quenching. Additionally, it was found that Al 10 O 3 N 8 :Eu 2+ phosphor showed a strong blue emission under 147 nm excitation and shorter decay time compared with BAM:Eu 2+ phosphor, making it a potential phosphor used in plasma display panels. Si–N doping was performed to further increase the luminescence intensity of Al 10 O 3 N 8 :Eu 2+ phosphor and the related mechanism was discussed. Prospectively, it was feasible to apply the synthesis approach to other hardly achieved materials. [ABSTRACT FROM AUTHOR]

Abstract: Eu2+–Mg2+ co-doped alon phosphors were successfully prepared by carbothermal reaction at 1600°C for 2h and their structure and photoluminescence properties were studied. The lattice parameter increased with increasing Eu concentration, indicating the incorporation of Eu into alon crystal lattice. The pure alon phase was obtained when Eu concentration is below 0.2%. Compared with solid state reaction process, this method lead to less amounts of secondary phase, larger amounts of Eu2+ against Eu3+, smaller particle size, narrower particle size distribution and stronger luminescence intensity. The absolute emission intensity of obtained phosphor reached 82% relative to that of famous BAM: Eu2+ phosphor. The emission could be tuned widely from blue to green by varying carbon content. [Copyright &y& Elsevier]

Different fluxes had been used in the preparation of AlN:Eu2+ blue phosphors by the carbothermal reduction method. The influence of these fluxes on the phase composition, crystallinity, particle size, and photoluminescence (PL) of the produced phosphors was investigated. X-ray diffraction and microstructure characterizations showed that both CaF2 and BaF2 were excellent nitridation promoters for the synthesis of AlN:Eu2+ phosphors, because pure and highly crystallized AlN was obtained with 3 wt% fluxes. The use of CaF2 flux resulted in phosphors which featured a very weak blue shift emission due to lattice distortion and lattice imperfection caused by the incorporation of Ca into the AlN host, according to the results of IR spectra, decay curves, and the changes in lattice parameters. In comparison with phosphors produced without the use of fluxes, the use of BaF2 flux resulted in phosphors with higher PL intensity by a factor of 2.4, which were produced at lower soaking temperature and shorter soaking time. Finally, a simple reaction mechanism for the nitridation process was also suggested. [ABSTRACT FROM AUTHOR]

In this work, Eu-doped La 3 Si 8 N 11 O 4 phosphors with different doping concentrations are fabricated by solid state reaction method. A broad and asymmetric emission band that covers the wavelength range of 425–550 nm is observed. X-ray diffraction Rietveld refinement and X-ray absorption near edge structure (XANES) analyses reveal the co-existence of both trivalent and divalent states of Eu. By coating the phosphor particles with an ultrathin carbon layer using CVD technique, followed by an annealing in N 2 at 1600 °C, the trivalent ions Eu3+ are reduced to Eu2+, resulting in a significant enhancement of quantum efficiency, both internal and external, and absorption efficiency. The application of the La 3 Si 8 N 11 O 4 :Eu in white light-emitting diodes is tested by coating the phosphor onto a near-UV LED chip in combination with the red-, green- and blue-emitting phosphors ([Ca, Sr]AlSiN 3 :Eu, ®-Sialon:Eu and BaMgAl 10 O 17 :Eu, respectively). It is demonstrated that the presence of the La 3 Si 8 N 11 O 4 :Eu phosphor significantly enhances the color rendering index of the device, showing its great potential for wLEDs applications. • The microstructure evolution of La 3 Si 8 N 11 O 4 : Eu phosphor was clarified in detail. • Both trivalent and divalent states of Eu exist in La 3 Si 8 N 11 O 4 : Eu. • Eu3+ was reduced to Eu2+ by carbon coating and annealing. • The highest quantum efficiency was achieved in the treated phosphors. [ABSTRACT FROM AUTHOR]

Mono-phase La 2 Si 6 O 3 N 8 :Ce 3+ phosphors co-doped with Tb 3+ were produced via a direct silicon nitridation (DSN) method at 1500 °C. The produced phosphors were characterized with regards to their crystalline structure, microstructure, photoluminescence properties, and lifetime. The decay mode of Ce 3+ suggests that energy transfer occurs in La 2 Si 6 O 3 N 8 :Ce 3+ ,Tb 3+ phosphors. Intense green emission was recorded from La 1.4 Si 6 O 3 N 8 :0.2Ce 3+ ,0.4Tb 3+ and qualifies these phosphors for further consideration as promising candidates for ultraviolet convertible phosphors in light-emitting devices. [ABSTRACT FROM AUTHOR]

The Eu2+-doped G-La 2 Si 2 O 7 phosphor was successfully prepared through the high-temperature solid-state reaction method with the aid of AlF 3 flux. The results of Eu L 3 -edge XANES characterization showed that only Eu3+ can be detected in as-received G-La 2 Si 2 O 7 phosphor and that Al 2 O 3 addition leads to a partial reduction of Eu3+ to Eu2+, while complete reduction occurs with AlF 3 addition. The obtained Eu2+-doped G-La 2 Si 2 O 7 phosphor exhibited typical Eu2+ blue-green emission under the near-UV light excitation. The analysis of Fourier transform infrared spectroscopy (FT-IR) and 27Al nuclear magnetic resonance (NMR) results suggests that Al occupies the Si sites and F occupies the O sites. The positive influence of Al–F doping is related to the structure of the produced phosphors, which was analyzed with the aid of first-principles density functional calculations. The results of the theoretical calculations are a good match to the experimental findings. • A novel blue-green emitting phosphor G-La 2 Si 2 O 7 :Eu2+ was synthesized. • With AlF 3 addition, the phosphor has occurred the complete reduction of Eu3+ to Eu2+. • The theoretical calculations are a good explanation to the experimental findings. [ABSTRACT FROM AUTHOR]