Synthesis, crystal structure and photoluminescence of novel blue-emitting Eu²⁺-doped (SiC)_x–(AlN)_1−xphosphors by a nitriding combustion reaction

Abstract

Graphical Abstract:Highlight: Novel blue-emitting (SiC) x -(AlN) 1-x :yEu 2+ phosphors were synthesized by nitriding combustion reaction, and their luminescence properties, thermal stability and possible doping site of Eu 2+ in (SiC) x -(AlN) 1-x lattice were investigated. AbstractNovel blue-emitting phosphors with the chemical composition of (SiC) x -(AlN) 1-x :yEu 2+ (x=0.06-0.50, y=0.001-0.01) were synthesized by a nitriding combustion reaction route, and the crystal structure, luminescence properties and thermal stability of the (SiC) x -(AlN) 1-x :yEu 2+ phosphors were investigated by theoretical and experimental approaches. Fist-principles calculation results prove that the solid solution of SiC with AlN promotes the doping of Eu 2+ ions into the (SiC) x -(AlN) 1-x host lattice, and Eu 2+ ions tend to occupy Al sites of the host. The synthesized (SiC) x -(AlN) 1-x :yEu 2+ phosphors absorb light in the region of 250-425 nm and show a single and symmetric broadband emission centered at about 470 nm due to the 4f 6 5d-4f 7 transitions of Eu 2+ . The luminescence intensity increases with the SiC content and reaches its maximum at x=0.20. The critical quenching concentration of Eu 2+ in the (SiC) 0.20 -(AlN) 0.80 :yEu 2+ phosphor is about y=0.006. The composition-optimized (SiC) 0.20 -2 (AlN) 0.80 :0.006Eu 2+ phosphor shows a small thermal quenching, retaining the luminance of 91.1% at 150 °C. The CIE coordinates were measured as (0.135, 0.167) with high color purity.The above results indicate that (SiC) x -(AlN) 1-x :yEu 2+ is a promising candidate as a blue-emitting ultraviolet convertible phosphor for white LEDs, and the combustion reaction route is expected to be applicable to synthesis of the present and other kinds of nitride phosphors. IntroductionWhite light emitting diodes (LEDs) have attracted increasing attention as a promising light source for solid state lighting due to their long lifetime, high luminous efficiency, energy saving, and environmental friendly characteristics. 1-3 Typically, commercial white LEDs can be generated by the combination of a blue LED chip and the famous yellow phosphor, YAG:Ce 3+ . 4 However, the disadvantages of this method are a low color-rendering index (CRI) and high correlated color temperature (CCT) due to red emission deficiency in the visible spectrum.During the last several years, white LEDs fabricated by using ultraviolet (UV)/near-ultraviolet (n-UV) chips coupled with blue, green and red phosphors have attracted much attention because of the advantageous of color stability and excellent color rending. 5-7 Therefore, the exploration of novel phosphors with strong absorption, desirable emission/excitation, and high efficiency under UV/n-UV excitation plays an important role in the development of white LEDs.Furthermore, low fabrication cost, low thermal quenching as well as high chemical stability are also required for the phosphors.As a highly efficient activator with allowed 4f-5d transitions, Eu 2+ ion has been widely investigated for the rare-earth-doped phos...

Recent progress in luminescence tuning of Ce3+and Eu2+-activated phosphors for pc-WLEDs

“…Similar work was reported by Shi et al and Xie et al on the (SiC) x -(AlN) 1Àx :Eu 2+ solid-solution phosphors by replacing Al 3+ -N 3À by Si 4+ -C 4À . 140,141 The (SiC) x -(AlN) 1Àx :Eu 2+ (x = 0-1) phosphor shows broad absorption bands in the 250-425 nm range, and bright blue emissions peaking at 470 nm, which has a more high color purity (0.135 and 0.167) for the x = 0.5 sample than that of the AlN:Eu 2+ sample. 140 Interestingly, the luminescence intensity increases with the SiC content and reaches its maximum at x = 0.20.…”

“…The modified SASF:Ce 3+ phosphors have wider emission peaks than SAF:Ce 3+ , which allows SASF:Ce 3+ phosphors to provide a higher color rendering properties when incorporated into an LED chip. 140 Interestingly, the luminescence intensity increases with the SiC content and reaches its maximum at x = 0.20. Other contributions originate from the increasing nephelauxetic effect offered by O 2À than F À in the lattice (different Sr sites) as x increases.…”

“…17b). 140,141 The (SiC) x -(AlN) 1Àx :Eu 2+ (x = 0-1) phosphor shows broad absorption bands in the 250-425 nm range, and bright blue emissions peaking at 470 nm, which has a more high color purity (0.135 and 0.167) for the x = 0.5 sample than that of the AlN:Eu 2+ sample. The emission red-shift is partially attributed to increasing distortion of the Ce 3+ sites, which causes an increased crystal field splitting.…”

“…The emission red-shift is partially attributed to increasing distortion of the Ce 3+ sites, which causes an increased crystal field splitting. 140 The reason is that the formation of (SiC) x -(AlN) 1Àx solid solution promotes the doping of Eu 2+ ions into Al sites of the host. Note that there is a non-monotonic increase of the excitation wavelength maximum with varying x.…”

Critical Review—Narrow-Band Emission of Nitride Phosphors for Light-Emitting Diodes: Perspectives and Opportunities

“…17a). 68,69 SiC integrates itself albeit in different mechanisms, whereby Si and C simultaneously dissolve. Herein, C atoms replaced N. Therefore, the evolution of the solid solution manifested through the c-axis compression with Si-condensed layer formation and the Eu-doped layer that further shrunk the ab plane.…”