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Abstract: Tunable white light of Eu2+ doped SiAlON crystal/glass composite phosphor with blue-yellow dual-emissions was demonstrated by variation of excitation wavelength in this work. The excitation properties of blue emission originated from the transition of Eu2+ ions in the Si–Al–B–O–N glass matrix and that of yellow emission originated from the transition of Eu2+ ions in the SiAlON lattice were investigated, respectively. By varying the excitation wavelength in the range of 330–380nm, white emission was tuned from cool white to warm white for this SiAlON crystal/glass composite phosphor owing to the various excitation properties of these two emission bands. Presented results indicate that this tunable SiAlON crystal/glass composite white-light phosphor might be applied in white LED, combining with UV chips with different emitting wavelengths in the range of 330–380nm. [Copyright &y& Elsevier]

Abstract: Cerium-doped Ca–α-SiAlON phosphors with Ca n−1.5x Si12−m−n Al m+n O n N16−n :Ce x (m=2n, 0.8≤m≤2.4, and 0.02≤x≤0.40) nominal compositions have been synthesized by gas pressure sintering (GPS). The photoluminescence (PL) properties were studied in relation to phase composition, particle morphology, and microstructure. Continuous addition of Ce rare-earth (RE) could enhance the emission intensity of phosphors, which was partially attributed to the formation of increased amount of planar defects where dense doping of Ce ions is achieved. Such enhancement could hold up to x=0.32, above which the emission intensity fell slightly due to the formation of more secondary phases and a surface glassy phase rather than concentration quenching. Finally, possible ways to improve the luminescence properties of Ce-doped α-SiAlON phosphors were discussed through tailoring the composition and microstructure. [Copyright &y& Elsevier]

Abstract: Tricolor emission in a same Ca3Si2O7 host with independent Ln (LnCe3+, Eu2+, Tb3+) dopants is demonstrated to construct a near-UV white light emitting diode (LED). The luminescence properties and thermal quenching properties, as well as the applications in near-UV white LED are investigated. These phosphors show typical blue, red, and green, three-basal-color, luminescence in the CIE chromaticity diagram for Ce3+, Eu2+ and Tb3+ dopants, respectively. Thermal quenching properties show that the luminescence thermal stability strongly depends on the different dopant types; better thermal quenching property of Ce3+ and Tb3+ is recorded in comparison with that of Eu2+. The white LED prototype fabricated with near-UV chip and as-prepared tricolor phosphors exhibits acceptable CIE chromaticity coordinates (0.32, 0.30) with a CCT of 6000K and a CRI of 87, indicating the potential application of Ca3Si2O7:Ln phosphors in near-UV white LED. [Copyright &y& Elsevier]

The role of Si in the valence state of Ce and phase control in YAG:Ce phosphors was investigated upon incorporation of Si-O in the form of SiO. By varying the amount of SiO addition, the valence state of tetravalent and trivalent Ce ions was identified distinctly by X-ray photoelectron spectroscopy and the phase purity of YAG host phase was examined by X-ray diffraction patterns. The self-reduction phenomena from Ce to Ce in YAG:Ce samples was observed to be featured in a typical 5d → 4f yellow-green transition of Ce ion upon firing in air, driven by charge compensation for imbalance substitution of Ce for Y. The addition of SiO promotes further reduction of Ce to Ce in an amount up to 7.0 wt%, owing to spontaneous charge compensation, and suppresses the formation of YAP (yttrium aluminate perovskite, YAlO) and YAM (yttrium aluminate monoclinic, YAlO). The results reveal the role of SiO addition in a proper amount to be able to achieve desired luminous center of Ce and phase-pure YAG for a series of YAG hosted luminescence materials such as blue-excitable YAG phosphor or laser-pumped YAG-based transparent ceramics or glass ceramics for lighting and display purposes. [ABSTRACT FROM AUTHOR]

Abstract: White light emission (Sr0.85Mg0.14)3(P1−x Si x O4)2: Dy3+ phosphors applied for white light emitting diodes (LEDs) were synthesized by the solid state reaction process. The phases and luminescence properties of the obtained (Sr0.85Mg0.14)3(P1−x Si x O4)2: Dy3+ phosphors were well characterized. The presented results demonstrate that the (Sr0.85Mg0.14)3(P1−x Si x O4)2: Dy3+ particles emit an intensive white light emission under excitation at 350nm. Additionally, the effect of Si4+ incorporation concentration on the luminescence properties of (Sr0.85Mg0.14)3(PO4)2: Dy3+ was investigated in detail. [Copyright &y& Elsevier]

Abstract: Novel Eu2+ doped SiAlON-crystal/glass composite white-light-emitting phosphor applied in ultraviolet (UV) based white light-emitting-diode (LED) was prepared by a facile strategy instead of traditional recrystallization procedure. Blue-emitting glass phase was introduced in yellow-emitting α-SiAlON:Eu2+ micron-crystal phosphor by simple heat-treatment with the addition of nano-SiO2 or B2O3. As a result, white-light emission with CIE chromaticity coordinates (0.31, 0.33) and (0.32, 0.37) was demonstrated by mixing blue and yellow light for B2O3 and SiO2 induced crystal/glass composite phosphor, respectively. This variety of white-light-emitting phosphors in such a crystal/glass composite structure shows potential applications in UV white LED to be free of complicated multicomponent phosphor blending operation. [Copyright &y& Elsevier]

In this paper, color-tunable emission of Eu 2+ doped Calcium-phosphate based phosphors resulted from the phase evolution of luminescent host was demonstrated. Red emission peaked at 675 nm was tuned to blue emission peaked at 480 nm as the Calcium-phosphate luminescent host evolved from Ca 4 (PO 4 ) 2 O (TTCP) to α-Ca 3 (PO 4 ) 2 (α-TCP) by increasing calcination temperature from 1400 °C to 1500 °C. The phase transformation and the resultant color-tunable emission as well as the dependence of emission on phase composition for Calcium-phosphate based phosphors were investigated in detail. The results presented a promising approach to tailor the luminescent properties for phosphors materials by means of phase evolution of hosts. [ABSTRACT FROM AUTHOR]

Abstract: Novel single-phased white-light-emitting Ca2.96(P0.99B0.01O4)2:0.04Dy3+ phosphors for light-emitting diode (LED) applications were synthesized by conventional solid-state reactions. The phases and luminescent properties of the obtained Ca2.96(P0.99B0.01O4)2:0.04Dy3+ phosphors were well characterized. The results show that the excited bands of Ca2.96(P0.99B0.01O4)2:0.04Dy3+ phosphor centered at wavelengths of 324nm (6H15/2→4M17/2), 350nm (6H15/2→4M15/2, 6P7/2), 366nm (6H15/2→4I11/2), 387nm (6H15/2→4I13/2, 4F7/2), 427nm (6H15/2→4G11/2), and 448nm (6H15/2→4I15/2). On excitation at 350nm, the emission transitions of Dy3+ consisted of double emission bands, which can be assigned to the transition emissions of 4F9/2→6H15/2 (480nm) and 4F9/2→6H13/2 (572nm). One mol% B3+ dopant improved the luminescence intensity of Ca2.96(PO4)2:0.04Dy3+ phosphor, and the reason was proposed. The developed phosphor has great potential as a single-component white-light-emitting phosphor for UV-light-emitting diodes. [Copyright &y& Elsevier]

A novel red-emitting phosphor NaLaMgWO 6 (NLMWO):xMn4+ has been synthesized by a high-temperature solid-state reaction. The samples were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence excitation (PLE) and emission (PL) spectra. The results indicated that the phosphors could be efficiently excited by the near ultraviolet (NUV) and blue light. Due to the 2E g → 4A 2g transition of Mn4+ ion, the samples can exhibit red emission, which was consistent with the absorption spectrum required for plant growth. In addition, the concentration quenching mechanism was dipole-quadrupole (d-q) interaction of Mn4+ activator, when the optimal doping concentration of Mn4+ was determined to be 30 mol%. Moreover, the influence of Mn4+ and Al3+ ions co-doped on the PL properties of NLMWO were studied. The PL intensity of NLMWO:0.001Mn4+, 0.002Al3+ is 1.77 times than that of NLMWO:0.003Mn4+ phosphor. The results illustrated that the PL intensity of phosphors can be greatly improved via charge compensation. The obtained results validated that NLMWO:Mn4+ can be used as a new type of red luminescent powder absorbed by plant photosensitive pigment P FR to promote plant growth. • NLMWO:Mn4+ can be used as a new red luminescent powder absorbed by P FR. • The PL intensity of NLMWO:0.001Mn4+, 0.002Al3+ is increased by 1.77 times. • The PL intensity of phosphors can be greatly improved via charge compensation. [ABSTRACT FROM AUTHOR]

A novel-far red emission Li 6 CaLa 2 Sb 2 O 12 (LCLSO):Mn4+ phosphor was prepared by traditional high temperature solid state reaction method. The morphology, spectral characteristics and luminescence properties of the phosphors were all studied systematically. Based on the results, when x = 0.0045 (x represents the doping concentration of Mn4+), the emission intensity of LCLSO: x Mn4+ phosphor reaches the maximum, and the concentration quenching occurs after the Mn4+ doping concentration exceeds 0.0045. In addition, the effect of Al3+-doped on the luminescent properties of the materials was also studied. The optimum doping concentration of Al3+ is y = 0.009 (y represents the doping concentration of Al3+), and the luminescence intensity of Mn4+ can be increased about 4 times. Moreover, the integrated luminescence intensity, the thermal activation energy, and decay time can be obtained via calculation. In summary, LCLSO:Mn4+, Al3+ phosphor exhibits good luminescence efficiency and thermal stability, and possesses the latent application foreground in plant growth lighting. • Li 6 CaLa 2 Sb 2 O 12 :Mn4+ far-red phosphors were prepared by high temperature method. • Al3+-doped can lead to better luminescent properties of the LCLSO:Mn4+ phosphor. • The emission of LCLSO:Mn4+,Al3+ matches well with the absorption spectrum of P FR. [ABSTRACT FROM AUTHOR]

A series of novel Mn4+-activated double perovskite antimonate Sr 2 LaSbO 6 (SLSO) far-red emitting phosphors were successfully synthesized by a high-temperature solid-state method. X-ray diffraction (XRD), photoluminescence excitation (PLE) and emission (PL) spectra, temperature-dependent photoluminescence spectra, CIE chromaticity coordinates, as well as internal quantum efficiency (IQE) were used to analyze these phosphor samples. Under 334 nm excitation, the SLSO:Mn4+ phosphors emit far red emission peaking around 694 nm due to the Mn4+: 2E g →4A 2g transition. The optimal doping concentration of Mn4+ was 0.8 mol%, moreover, the critical distance (R c) was 40.89 Å. The dipole-quadrupole interaction may be responsible for the concentration quenching mechanism of Mn4+ ions in the SLSO:Mn4+ phosphors. Furthermore, various Al3+ improved SLSO:0.008Mn4+ phosphors are investigated. When Al3+ is doped with 0.8%, the PL intensity increased by 2.92 times. In addition, the IQE of SLSO:0.008Mn4+ and SLSO:0.008Mn4+, 0.008Al3+ were found to be as high as 35.2% and 38.1%, respectively. Impressively, all chromaticity coordinates of samples located in far-red region. Therefore, these superior luminescence properties of SLSO:Mn4+ sample demonstrated its potential applications in plant cultivation and growth light-emitting diodes (LEDs). • Far-red emit phosphors Sr 2 LaSbO 6 :Mn4+ were synthesized by solid state reaction method. • For SLSO:Mn4+ phosphor, the optimal doping concentration of Mn4+ is 0.8%. • The activation energy (E a) of SLSO:0.008Mn4+ is 0.353 eV. • The PL intensity of SLSO:0.008Mn4+, 0.008Al3+ is 2.92 times that of SLSO:0.008Mn4+. [ABSTRACT FROM AUTHOR]

A series of Ca 2 La 8 (SiO 4) 6 O 2 :Eu3+ (CLSO:Eu3+) and Ca 4 La 6 (SiO 4) 4 (PO 4) 2 O 2 :Eu3+ (CLSPO:Eu3+) oxyapatite phosphors have been prepared via traditional solid-state reaction process. The phase composition of phosphors was analyzed by X-ray powder diffraction (XRD), and the morphology was evaluated by scanning electron microscopy (SEM). The characteristic photoluminescence properties were evaluated by analysis of photoluminescence excitation (PLE) and emission (PL) spectra. In addition, the luminescence decay times and emission-temperature relationship were also characterized. The results indicated that the phosphors could be efficiently excited by the near ultraviolet (NUV) light and blue light, and they exhibited red light emission. Meanwhile, the average particle sizes of CLSO and CLSPO hosts are about 2∼8 μm. Moreover, the low symmetry C 3 or C s sites appropriate for Eu3+ in the CLSO and CLSPO hosts are benefit to 5D 0 → 7F 2 electric dipole transition, which leads to greater R/O values of CLSO: y Eu3+ than those of CLSPO: y Eu3+. All the obtained results suggested that the prepared phosphors have a potential for application in white light emitting diodes (WLEDs). • Novel CLSO:Eu3+/CLSPO:Eu3+ red phosphors have been successfully synthesized. • The optimal concentration of Eu3+ are 40 mol% (CLSO) and 60 mol% (CLSPO). • The E a of CLSO:0.4Eu3+ and CLSPO:0.6Eu3+ are 0.230 and 0.303 eV, respectively. • The PL intensity of CLSO:0.4Eu3+ is 1.29 times than that of CLSPO:0.6Eu3+. [ABSTRACT FROM AUTHOR]

The red oxide phosphors activated by Mn4+ have become a research hotspot because of their excellent physical/chemical stability, which can be applied in the field of light-emitting diodes (LED) plant growth lighting. Here, a new type of Sr 9 Gd 2 W 4 O 24 (SGWO):Mn4+ red phosphor was prepared by traditional high temperature solid state reaction method. The phase compositions and morphologies of powders were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The luminescent properties of the samples with varying Mn4+ concentrations were investigated, and the photoluminescence excitation (PLE) spectra illustrate that samples can be effectively excited by near-ultraviolet/blue light. Furthermore, typical concentration quenching occurs when the doping concentration of Mn4+ exceeds 0.4 mol%. In addition, the thermal activation energy of the sample was calculated to be 0.3641 eV. Importantly, under the excitation of near-UV light at 365 nm, SGWO:0.004Mn4+ phosphor can emit bright far-red light. All the results indicated that SGWO:Mn4+ phosphors have potential application value in indoor plant cultivation. • Tetratungstate Sr 9 Gd 2 W 4 O 24 :Mn4+ sample was synthesized by high temperature method. • SGWO:Mn4+ phosphor can emit far-red light under the 365 nm NUV excitation. • The PL of SGWO:Mn4+ match well with the absorption spectrum of phytochrome P FR. [ABSTRACT FROM AUTHOR]

A novel far-red emission NaLa 2 SbO 6 (NLSO):Mn4+ phosphor was prepared by traditional high temperature solid state reaction method. In the range of 200–600 nm, NLSO:Mn4+ phosphors exhibit broad excitation band centered at 322 nm and 498 nm. Under the excitation of 322 nm, the phosphor exhibits a far-red emission band centered at 707 nm in the range of 600–800 nm. In NLSO:Mn4+ phosphors, the optimum doping concentration is x = 0.003. In addition, the effect of Al3+-doped on the luminescent properties of the materials was also studied. The optimum doping concentration of Al3+ is x = 0.004, and the luminescence intensity of Mn4+ can be increased by 53%. In addition, NLSO:0.003Mn4+, 0.004Al3+ phosphors have high internal quantum efficiency and good thermal stability. The CIE chromaticity coordinates of NLSO:0.003Mn4+, y Al3+ phosphors are calculated, and which are located in the far-red region. All the results show that the synthesized phosphors have great application prospects in plant cultivation. • Novel-type far-red emit phosphors NaLa 2 SbO 6 (NLSO):Mn4+ were synthesized by solid state reaction. • When the doping concentration of Al3+ is 0.4%, the PL intensity of NaLa 2 SbO 6 :Mn4+, Al3+ reaches the maximum. • At 423 K, the PL intensity of NaLa 2 SbO 6 :0.003Mn4+ decreased to 42.75% of the initial PL intensity. • The activation energy (E a) of NaLa 2 SbO 6 :0.003Mn4+ and NaLa 2 SbO 6 :0.003Mn4+, 0.004Al3+ are 0.355 eV and 0.392 eV, respectively. [ABSTRACT FROM AUTHOR]