The Effects of Fluxes on AlN:Eu²⁺Blue Phosphors Synthesized by a Carbothermal Reduction Method

Abstract

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.

Synthesis of AlN: Eu2+ green phosphors by a simple direct nitridation method

“…The photoluminescence intensity increased with Eu concentration, peaking at 0.5% Eu doping, as shown in Figure (b), in agreement with earlier reports . However, further increases in Eu 2+ resulted in a decrease in the photoluminescence intensity, mainly because of concentration quenching.…”

“…[8,9] Because of its simplicity and relatively low cost, carbothermal reduction-nitridation is used to prepare AlN: Eu phosphors, [10] but the residual carbon contamination decreases the luminescence intensity and fluxes such as BaF 2 are added to improve the luminescence properties. [11] The gas reduction-nitridation method, which uses NH 3 and hydrocarbon compounds (typically C 3 H 8 ) as reactant gases, has also been reported to synthesize AlN powders or fiber. [12][13][14] Owing to the high reactivity of ammonia, AlN can form at lower temperatures and residual carbon can be avoided.…”

Improved Blue‐Emitting AlN:Eu2+ Phosphors by Alloying with GaN

“…Recently, blue‐emitting AlN:Eu 2+ and AlN:Ce 3+ phosphors obtained by Si codoping were successfully prepared by a gas pressure sintering method . In our previous study, we also obtained a pure AlN phase with Eu doping and presented detailed information about the exact location and luminescence mechanism of Eu in the AlN crystal lattice . It was demonstrated that pure AlN:Eu phosphor can be obtained by a gas‐reduction–nitridation method, which showed many good characteristics including high purity, free carbon residues, and low synthesis temperature.…”

Synthesis of High‐Performance BaMgAl10O17:Eu2+ Phosphor Through a Facile Aqua‐Suspension Method

“…However, a high calcination temperature of 1600°C leads to the decreasing luminescence intensity, which could be explained by the large agglomerates shown in Fig. c …”