MSi2O2−δN2+2/3δ:Eu (M=Sr, Ba) phosphors for field emission displays

New Polymorph of the Highly Efficient LED-Phosphor SrSi2O2N2:Eu2+ – Polytypism of a Layered Oxonitridosilicate

“…The reflection positions in powder X-ray diffraction (PXRD) patterns, in principle, resemble those reported by Zhu ( X 2 -phase) and Hintzen although these authors have proposed different metrics. However, some powder patterns of our samples and also those in the literature show a number of reflections that are inconsistent with the triclinic structure model of SrSi 2 O 2 N 2 discussed in the literature. ,,,,− Surprisingly, samples with such ”impurity phases” exhibit excellent overall luminescence properties. Whenever peak emission wavelengths of SrSi 2 O 2 N 2 :Eu 2+ powder samples are reported to be significantly smaller than 537 nm the corresponding PXRD patterns show unknown, additional reflections. ,,,,, In this contribution, we clarify the nature of the additional phase that leads to these reflections and further investigate its impact on luminescence properties.…”

“…Regarding the enhancement of color rendition of white-light pc-LEDs that make use of mixtures of green and red emitting phosphors, a shift of the peak emission wavelength toward shorter wavelengths (∼530 nm) would be desirable . The color point of “triclinic” SrSi 2 O 2 N 2 :Eu 2+ can be changed by variation of the Eu-doping level ,,− , or substitution of Sr by Ca or Ba. ,,,,,− Nevertheless, all changes of the host-lattice composition shift the emission wavelength toward smaller energies. For Sr 1‑ x Ba x Si 2 O 2 N 2 :Eu 2+ with x ≥ 0.75, a shift to higher energies can be achieved; however, its emission spectrum is located in the blue-green spectral region due to the different structure type. , The determination of luminescence properties of monoclinic SrSi 2 O 2 N 2 :Eu 2+ cannot be done using powder samples because all obtained samples were inhomogeneous (see section: Rietveld refinement).…”

“…SrSi 2 O 2 N 2 is a host lattice showing excellent luminescence properties when doped with Eu 2+ . SrSi 2 O 2 N 2 :Eu 2+ exhibits intense broad-band emission in the yellow-green spectral region due to the parity allowed 4f 6 ( 7 F)5d 1 → 4f 7 ( 8 S 7/2 ) transition when excited by UV to blue light. ,,− The disordered crystal structure consists of alternating metal-ion and silicate layers. Both the idealized ordered structure as well as the average structure of the disordered variant are triclinic ( a = 7.0802(2), b = 7.2306(2), c = 7.2554(2) Å, α = 88.767(3), β = 84.733(2), γ = 75.905(2)°, V = 358.73(2) Å 3 , space group P 1).…”

Recent progress in low-voltage cathodoluminescent materials: synthesis, improvement and emission properties

“…For example, the rare earth ions activated semiconductor materials and (oxo)nitridosilicates are possible selections. 5,13,43,272 The use of coatings can also yield excellent stability to the phosphors when exposed to moisture and other atmospheric components, and to protect phosphors from irradiation damage. For example, Xu et al 67 investigated the degradation properties after mixing the representative Lu 3 Ga 5 O 12 :Tb 3+ phosphor with In 2 O 3 nanoparticles.…”

The effect of electron cloud expansion on the red luminescence of Sr4Al14O25:Mn4+ revealed by calculation of the Racah parameters

“…The white light-emitting diodes (WLEDs) show superiorities in terms of low energy consumption, high luminescence efficiency, eco-friendship without mercury pollution, long duration, unbreakable (in contrast to glass bulbs and tubes) with solid-state encapsulation, and easy transportation and installation over than traditional incandescent and fluorescent lamps, while the red phosphor is essential to obtain warm white light with high color rendering index (CRI) and low color temperature for home lighting [1][2][3][4][5][6]. The phosphor activated by Mn 4+ is a promising candidate for WLEDs application, because the narrow lines of Mn 4+ emission could enhance the luminous efficacy of radiation (LER) and the CRI given in units of lumens per watt of radiometric power (lm/ Wrad) [7].…”