“…As reported by Wang at al . 27 , Ca 3 Si 2 O 4 N 2 is composed of 12-membered rings of [SiO 2 N 2 ] tetrahedra. Similar12-membered rings are also found in the three refined structures.…”
Section: Resultsmentioning
confidence: 99%
“…Viewing perpendicularly to the octahedral plane, one can see that the coordination octahedron is highly symmetric when x = 1, while the symmetry of the octahedron decreases with reduction of x due to lattice distortion. It’s worth noting that although there are seven different car sites in the whole structure 27 , distortion is believed to occur on all the Ca sites. Structure evolution mentioned above would have an important influence on the luminescence properties of the title phosphor.Figure 3Schematic structure evolution of Ca 2.97 Si 3− x O 3+ x N 4−2 x : 0.03Eu 2+ phosphors depending on x values ( x = 0, 0.5 and 1, respectively).…”
Section: Resultsmentioning
confidence: 99%
“…Later, XM Wang et al . 27 discussed the O/N ordering and discovered that this interesting phase is composed of corrugated 12-membered ring structure. Although several reports on photoluminescence properties of Eu 2+ or Ce 3+ doped Ca 3 Si 2 O 4 N 2 have been published in recent years, research on this potential host as a phosphor is still at a primary stage 28–30 .…”
Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca3Si3−xO3+xN4−2x: Eu2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca3Si3−xO3+xN4−2x: Eu2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.
“…As reported by Wang at al . 27 , Ca 3 Si 2 O 4 N 2 is composed of 12-membered rings of [SiO 2 N 2 ] tetrahedra. Similar12-membered rings are also found in the three refined structures.…”
Section: Resultsmentioning
confidence: 99%
“…Viewing perpendicularly to the octahedral plane, one can see that the coordination octahedron is highly symmetric when x = 1, while the symmetry of the octahedron decreases with reduction of x due to lattice distortion. It’s worth noting that although there are seven different car sites in the whole structure 27 , distortion is believed to occur on all the Ca sites. Structure evolution mentioned above would have an important influence on the luminescence properties of the title phosphor.Figure 3Schematic structure evolution of Ca 2.97 Si 3− x O 3+ x N 4−2 x : 0.03Eu 2+ phosphors depending on x values ( x = 0, 0.5 and 1, respectively).…”
Section: Resultsmentioning
confidence: 99%
“…Later, XM Wang et al . 27 discussed the O/N ordering and discovered that this interesting phase is composed of corrugated 12-membered ring structure. Although several reports on photoluminescence properties of Eu 2+ or Ce 3+ doped Ca 3 Si 2 O 4 N 2 have been published in recent years, research on this potential host as a phosphor is still at a primary stage 28–30 .…”
Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca3Si3−xO3+xN4−2x: Eu2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca3Si3−xO3+xN4−2x: Eu2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.
“…Several compounds are known in literature for the systems Ca–Si–N and Ca–Si–O–N [e.g., CaSiN 2 , Ca 2 Si 5 N 8 , HP‐Ca 2 Si 5 N 8 , Ca 4 SiN 4 , Ca 5 Si 2 N 6 , CaSi 2 O 2 N 2 ,, Ca 3 Si 2 O 4 N 2 and Ca 2 Si 3 N 4 O 2 , CaSi(O/N) 2 ]. The systems MSiN 2 (M = Mg, Ca, Sr, Ba) in general stand out due to their multifaceted application in industry as, for example, sinter additives for Si 3 N 4 ceramics or Eu 2+ ‐doped LED‐phosphors, …”
Section: Introductionmentioning
confidence: 99%
“…In the meantime several reports appeared concerning these cubic Ca‐phases (with a lattice parameter of ca. 15 Å) with or without oxygen insertion , . Hick et al proposed that the cubic phase of CaSiN 2 described in literature is actually Ca 16 Si 17 N 34 , while Wang and Sharafat determined the structure with composition Ca 3 Si 2 O 4 N 2 and Ca 3– x Si 2 N 2–2 x O 4+2x ( x = 0.12), respectively.…”
HP‐CaSiN2 was obtained by HP/HT (high pressure / high temperature) synthesis utilizing the multianvil technique (4.5 to 18 GPa, 900 to 1200 °C) starting from the ambient pressure phase CaSiN2. Structure solution and Rietveld refinement were started with the cell parameters of HP‐CaSiN2 determined by selected area electron diffraction (SAED). The crystal structure of the high‐pressure phase was refined in space group Pbca (no. 61) with a = 5.1296(2), b = 10.2993(2), c = 14.5442(3) Å, V = 768.39 Å3, Z = 16, RBragg = 0.0484, Rw = 0.0256 and GoF = 1.0. HP‐CaSiN2 is built up by a three‐dimensional nitridosilicate network of vertex‐sharing SiN4‐tetrahedra with N bridging. The arrangement of the vertex‐linked tetrahedra in HP‐CaSiN2, being isostructural with KGaO2, is a tilting distortion of the stuffed β‐cristobalite type framework. Due to the high pressure the tilting angle of the SiN4‐tetrahedra has become much smaller so that the latter appear edge‐sharing sharing which is only a consequence of the chosen view along [100]. The Ca ions are located within these sechser‐ring channels and are coordinated by 6 and 7 N‐atoms, respectively. HP‐CaSiN2 is similar to CaSiN2, but differs clearly in the rotation of the SiN4‐tetrahedra and in the conformation of the sechser‐rings. Because of their coexistence HP‐CaSiN2 and CaSiN2 represent a very good example of an isosymmetric polymorphism.
Ce3+‐, Tb3+‐, and Dy3+‐activated Y4Si2N2O7 phosphors have been prepared by the Pechini‐type sol–gel method followed by ammonolysis of the precursors. The phase purity, morphology, crystallization condition, chemical composition, and thermal stability of the products have been studied carefully by X‐ray diffraction (XRD), energy‐dispersive X‐ray (EDX), scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), fourier‐transform infrared (FTIR), and thermogravimetry analysis (TGA) techniques. The photoluminescence (PL) and cathodoluminescence (CL) properties of Ce3+‐, Tb3+‐, and Dy3+‐doped Y4Si2N2O7 phosphors were also investigated. The electronic structure of Y4Si2N2O7 has been investigated by density‐functional theory methods. The calculations revealed that the nitrogen atom contributes more excited electrons than the O atom. The band gap has been calculated through the reflection spectrum of the Y4Si2N2O7 host. For Ce3+/Tb3+/Dy3+ singly doped Y4Si2N2O7 products, the phosphors give the typical emissions of the activators. The energy transfers from Ce3+ to Tb3+ and Dy3+ ions have been found and demonstrated through the PL spectra and luminescence decay times. The emission color of Y4Si2N2O7:Ce3+, Tb3+ and Y4Si2N2O7:Ce3+, Dy3+ samples can be tuned by energy transfer processes. Additionally, the temperature‐dependent PL properties and the degradation property of CL under continuous electron bombardment of the as‐synthesized phosphors prove that the Y4Si2N2O7 host has good stability. Therefore, the Y4Si2N2O7:Ce3+, Tb3+, Dy3+ phosphors could serve as a promising candidate for UV W‐LEDs and FEDs.
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