Search

Ce 3+ , Tb 3+ co-doped T-phase orthosilicate Ba 1.2 Ca 0.8 SiO 4 phosphors were prepared by means of solid state reactions. The synthesized samples were investigated using XRD and PL emission and excitation spectra. The emission spectra for Ce 3+ doped Ba 1.2 Ca 0.8 SiO 4 phosphors show broad bands in the 320–550 nm spectral region. The excitation spectra exhibit several absorption peaks in the range of 250–400 nm. Both the emission and excitation spectra are dependent on the excitation or monitoring wavelengths. We attribute these results to Ce 3+ ions occupying two different crystallographic sites (i.e., Ce I and Ce II). The Ce 3+ , Tb 3+ co-doped Ba 1.2 Ca 0.8 SiO 4 phosphors show Tb 3+ -related line emissions in the 475–600 nm spectral region and Ce 3+ -related band emissions in the 350–525 nm spectral region when the 4 f → 5d transition of Ce 3+ is excited (λ ex  = 345 nm), indicating that energy transfer from Ce 3+ to Tb 3+ takes place. Moreover, the emission intensity of 5 D 4 → 7 F 5 transition for Ba 1.00 Ce 0.02 Tb 0.08 Li 0.10 Ca 0.8 SiO 4 is 30 times stronger than that of Ba 1.04 Tb 0.08 Li 0.08 Ca 0.8 SiO 4 sample under 345-nm UV excitation. [ABSTRACT FROM AUTHOR]

A series of K 2 MgSi 3 O 8 : x Ce 3+ ( x = 0.01–0.09), K 2 MgSi 3 O 8 :0.05Ce 3+ , y Tb 3+ ( y = 0–0.09) phosphors was prepared by solid-state method. X-ray diffraction was used to determine the crystal phase. Luminescence properties were characterized by photoluminescence (PL), photoluminescence excitation (PLE) spectra at room temperature. K 2 MgSi 3 O 8 : x Ce 3+ series emits blue light when excited by UV-light (λ ex = 350 nm). Nonequivalent substitution of K + for Ce 3+ leads to the multiple Ce 3+ centers in the compound. K 2 MgSi 3 O 8 :Ce 3+ , Tb 3+ exhibits broad band emission of Ce 3+ and the characteristic line emission of Tb 3+ . The luminescence color could be tuned from blue (0.16, 0.10) to greenish blue (0.19, 0.26) by varying Tb 3+ content. The energy transfer has been confirmed to occur via quadrupole-quadrupole interaction. These results indicate that the K 2 MgSi 3 O 8 :Ce 3+ , Tb 3+ phosphor might be a promising material for w-LEDs application. [ABSTRACT FROM AUTHOR]

The luminescence properties of Eu 2+ in AgCa 10 (PO 4 ) 7 has been studied at room and low temperature and the decay times of Eu 2+ in this matrix have been measured and analyzed. According to the crystal structure of AgCa 10 (PO 4 ) 7 , photoluminescence (PL) spectra and decay curves, the substitution of Eu 2+ ions is possible to four different Ca 2+ sites. The red-shift of emission wavelength and energy transfer process between Eu 2+ activator ions are discussed. [ABSTRACT FROM AUTHOR]

This article reports on the optical properties of Sm3+-activated GdB3O6phosphors based on the measurement of their photoluminescence spectra and luminescence decay curves. Energy transfer from Gd3+to Sm3+and the concentration quenching of the Sm3+ion emission are investigated. From the photoluminescence spectra and decay curves, the energy transfer from Gd3+to Sm3+is confirmed. The concentration quenching of the Sm3+ion emission can be ascribed to resonant cross-relaxation. The interaction between the Sm3+ions is derived of the electric dipole–dipole type through fitting the data with the Inokuti-Hirayama model. The critical distances and energy transfer microparameter for the transfer processes are given. The decay curves of Sm3+4G5/2level exhibiting a buildup and decay process also confirm the energy transfer from Gd3+to Sm3+and between Sm3+ions. [ABSTRACT FROM PUBLISHER]

Highlights: [•] SrLiB9O15:Ce3+/Tb3+ phosphors were studied for the first time. [•] Ce3+ ions occupy two different sites (Ce I and Ce II) in SrLiB9O15 crystal. [•] Ce3+ ions substitute Sr2+ sites and interstitial sites simultaneously. [•] Energy transfer behavior from Ce3+ to Tb3+ is confirmed. [•] The energy transfer occurs from Ce II to Tb3+ in this case. [ABSTRACT FROM AUTHOR]

Abstract: Sn2+- and Sn2+/Mn2+-doped α-Sr2P2O7 phosphors have been synthesized by using the traditional solid-state reaction. The photoluminescence of Sn2+ and Sn2+/Mn2+ in α-Sr2P2O7 are reported and discussed. The Sn2+-activated material exhibits a blue-emitting band peaking at about 450nm under UV excitation. The Mn2+ emission peaking at about 565nm of Sn2+/Mn2+ co-doped samples can be enhanced through energy transfer from Sn2+ to Mn2+. Combining emission colors of Sn2+ and Mn2+ under UV excitation, white light emission can be achieved. [Copyright &y& Elsevier]

Highlights: [•] Emission spectrum at 20K confirms that Eu2+ ions occupy three sites. [•] Decay curves of three types of Eu2+ reflect the characteristics of energy transfer. [•] The Eu(I) emission is thermally quenched at 323K. [•] Ca3Mg3(PO4)4:Eu2+ has good thermal stability. [•] Ca3Mg3(PO4)4:Eu2+ is a promising phosphor for near UV excited white LEDs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lifetime of Gd decreases with Dy concentration, confirming energy transfer. [•] Rise time confirms the feeding of the Dy excited state by energy transfer. [•] Concentration quenching of Dy emission is ascribed to resonant cross-relaxation. [•] Interaction between Dy ions is dipole-dipole type through fitting with I-H model. [ABSTRACT FROM AUTHOR]

Abstract: (Gd1−x Eu x )(BO2)3 (0≤x≤1) phosphors are synthesized by traditional high temperature solid state reaction. The photoluminescence (PL) properties of Gd(BO2)3 and Gd(BO2)3 activated with Eu3+ are investigated. The PL spectra exhibit the typical characteristic emission and excitation of Gd3+ and Eu3+ ions, and support the energy transfer taking place from Gd3+ to Eu3+ ions. The relationship between Eu3+ doping concentration and emission intensity is also studied. Even if all of the Gd3+ ions are substituted by Eu3+ ions, the concentration quenching between Eu3+ happens. However, the quenching is not complete. The luminescence decay curves are measured, and the lifetimes become short with the Eu3+ content increasing. The decreasing Gd3+ lifetimes also indicates that there exists efficient energy transfer between Gd3+ and Eu3+ ions. [Copyright &y& Elsevier]

Abstract: Sr2Mg(BO3)2:Ce3+,Li+ and Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ phosphors have been synthesized by conventional solid state reaction technology at 900°C for 12h in reducing atmosphere. The phase purity, photoluminescence (PL) properties, thermal stability, energy transfer and luminescent decay curves have been investigated. Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ phosphors show blue and deep-red [1] For interpretation of color in Figs. 1–6, the reader is referred to the web version of this article. 1 emission bands. The deep-red emission band is attributed to the energy transfer from Ce3+ to Mn2+. The fluorescence lifetimes of Ce3+ in co-doped sample are shorter than that in single doped one, which confirms that the energy transfer takes place. The phosphors have weak thermal quenching. The luminescence properties of Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ make the phosphor a new bicolor emitting material. [Copyright &y& Elsevier]

Abstract: Sr2LiSiO4F co-doped with Ce3+, Mn2+ have been synthesized by means of solid state reactions. Their photoluminescence (PL) emission spectra, excitation spectra and the decay profiles of Ce3+ emission have been measured at room temperature. The emission peak around 410nm is ascribed to the 5d1 to 2F5/2 and 2F7/2 transitions of Ce3+ ions, while the peak around 680nm is ascribed to the 4T1–6A1 transition of Mn2+ ions. The decay rate of the 5d state within Ce3+ ion under 355nm laser excitation becomes faster with the increase of Mn2+ concentration. The analysis of the observed spectra confirms that there exists energy transfer from Ce3+ to Mn2+. [Copyright &y& Elsevier]

Abstract: Orange-emissive Ce3+/Eu2+ co-doped Sr3Al2O5Cl2 phosphors were synthesized by a solid-state reaction. The large overlap between the emission spectrum of blue Sr3Al2O5Cl2:Ce3+ and the excitation spectrum of orange Sr3Al2O5Cl2:Eu2+, and the shortening trend in lifetime of Ce3+ donors with increasing Eu2+ concentration in Sr3Al2O5Cl2:Ce3+, Eu2+ provide the strong evidence of energy transfer from Ce3+ to Eu2+ ions. It supports that the orange emission intensity of the optimal co-doped phosphor is 1.5 times stronger than that of single Eu2+-doped one. The Sr3Al2O5Cl2:Ce3+, Eu2+ phosphor is a promising orange-emitting phosphor for warm-white-light-emitting diode because of its effective excitation in the near ultraviolet range. [Copyright &y& Elsevier]

Abstract: Eu3+- and Tb3+-activated SrGdGa3O7 phosphors were synthesized by the solid-state reaction and their luminescence properties were investigated. Sr(Gd1− x Eu x )Ga3O7 and Sr(Gd1− x Tb x )Ga3O7 formed continuous solid solution in the range of x =0–1.0. Unactivated SrGdGa3O7 exhibited a typical characteristic excitation and emission of Gd ion. The SrGdGa3O7:xEu3+ and SrGdGa3O7:xTb3+ phosphors also showed the well-known Eu3+ and Tb3+ excitation and emission. The energy transfer from Gd3+ to Eu3+ and Tb3+ were verified by photoluminescence spectra. The dependence of photoluminescence intensity on Eu3+ and Tb3+ concentration were also studied in detail and the photoluminescence (PL) intensity of SrGdGa3O7:Eu and SrGdGa3O7:Tb were compared with commercial phosphors, Y2O3:Eu and LaPO4:Ce,Tb. The luminescence decay measurements showed that the lifetimes of Eu3+ and Tb3+ were in the range of microsecond. The energy transfer from Gd3+ to Tb3+ was also observed in decay curve. [Copyright &y& Elsevier]

Color-tunable luminescence in phosphors can be achieved in a number of ways. In this study, a series of Ce3+/Tb3+ singly doped and (Ce3+,Tb3+) doubly doped Sr 5 (BO 3) 3 F (SBOF) phosphors, having color point tuning properties, were synthesized by solid-state reaction. The emission color can be adjustable in two ways: by means of changing Ce3+ concentration or doubly doping Ce3+ and Tb3+ ions. The variation in the Ce3+ concentration in Ce3+ singly doped SBOF shows a red shift of the emission. The red shift can be assigned to energy transfer between Ce3+ ions at different sites. In the SBOF:Ce3+,Tb3+ samples, adjustable emission from blue to green can also be obtained by changing Tb3+ doping concentration when Ce3+ content is fixed under UV excitation. This is due to the energy transfer process from Ce3+ to Tb3+ in SBOF:Ce3+,Tb3+ phosphors. Moreover, the characteristic emission peak intensity of Tb3+ in the co-doped sample is enhanced by about 40 times compared with the single-doped Tb3+ phosphor under near-ultraviolet excitation. The potential application of this green-emitting phosphor in UV chip excited white LED was evaluated. [ABSTRACT FROM AUTHOR]

A detailed investigation on photoluminescence properties and energy transfer mechanism of Tb3+/Mn2+ singly doped and co-doped T-phase orthosilicate Ba 1.2 Ca 0.8 SiO 4 (BCS) phosphors, synthesized by conventional solid state reaction, is provided. All the samples were investigated by X-ray diffraction (XRD), photoluminescence spectroscopy and fluorescence decay curve. The Mn2+ emission intensity of BCS:Tb3+, Mn2+ is 28 times stronger than that of BCS:Mn2+. In addition, the emission color of BCS:Tb3+, Mn2+ phosphors can be tuned from green to orange-red by varying Mn2+ concentration. The efficient energy transfer from Tb3+ to Mn2+ is responsible for these phenomena. By employing the Inokuti–Hirayama model and Dexter's energy transfer theory, the dipole–dipole interaction is confirmed as the predominant multipolar effect in controlling this energy transfer process. • Tb3+/Mn2+ doped T-phase orthosilicate Ba 1.2 Ca 0.8 SiO 4 phosphors were synthesized. • Emission intensity of Mn2+ for BCS:Tb3+,Mn2+ is enhanced than that of BCS:Mn2+. • Energy transfer mechanism is confirmed based on I–H model and Dexter's theory. • Emission color of BCS:Tb3+,Mn2+ can be tuned from green to red-orange. [ABSTRACT FROM AUTHOR]

Ce3+, Tb3+ and Ce3+-Tb3+ activated Ba 3 Y 2 (B 2 O 5) 3 phosphors were synthesized by a sol-gel pyrolysis method. The synthesized phosphors were investigated using X-ray diffraction (XRD) analysis, photoluminescence emission and excitation spectra and luminescence decay curves. In the Ce3+ activated Ba 3 Y 2 (B 2 O 5) 3 samples, two different Ce3+ centers (marked as Ce(1) and Ce(2)) could exist. The Ba 3 Y 2 (B 2 O 5) 3 :Tb3+ phosphor shows some emission peaks at ∼350–650 nm among which the green emission peak at 540 nm is the strongest. For the Ba 3 Y 2 (B 2 O 5) 3 :Ce3+, Tb3+ co-doped phosphor, the existence of energy transfer process from Ce3+ center to Tb3+ center is confirmed and the interaction mechanism between Ce3+ and Tb3+ in Ba 3 Y 2 (B 2 O 5) 3 :Ce3+,Tb3+ system is dipole-dipole interaction based on Inokuti–Hirayama (I H) model. • PL properties of Ce3+, Tb3+ and (Ce3+-Tb3+) activated Ba 3 Y 2 (B 2 O 5) 3 were studied. • Ce3+ site occupancy is investigated. • Two different Ce3+ centers (Ce1 and Ce2) exist in Ba 3 Y 2 (B 2 O 5) 3 host lattice. • The energy transfer from Ce3+ center to Tb3+ center takes place. [ABSTRACT FROM AUTHOR]

New potassium gadolinium phosphate [K 3 Gd 5 (PO 4 ) 6 ] doped with Eu 3+ , Ce 3+ , Tb 3+ and co-doped with Ce 3+ and Tb 3+ phosphors were prepared by high temperature solid state synthesis. Phase purity of the powders was checked by X-ray powder diffraction. Luminescence and excitation spectra of samples were reported. In particular, the interaction mechanism between Eu 3+ ions was investigated in terms of the Inokuti–Hirayama model; it was found that the interactions between Eu 3+ can be assigned to dipole–dipole interaction. K 3 Gd 5 (PO 4 ) 6 :Eu 3+ could act as a candidate for solid state lighting due to its strong absorption band in the near-UV region (350–400 nm). The energy transfer from Ce 3+ to Tb 3+ was confirmed and the mechanism was studied using Dexter's theory; it is concluded that electric dipole–dipole interaction predominates in the energy transfer process from Ce 3+ to Tb 3+ in the K 3 Gd 5 (PO 4 ) 6 host. The energy transfer efficiency and critical distance were also investigated. [ABSTRACT FROM AUTHOR]

The luminescence property of phosphors plays an important role in the performance of phosphor-converted white light-emitting-diode (pc-WLED). In this paper, we report a simple energy-transfer (ET) strategy to enhance Tb3+ emission under near-UV excitation in Y 4 Zn 4 (SiO 4) 5 (YZS) doped with Ce3+/Tb3+ phosphor. The luminescence properties of YZS:Ce3+ based on crystal structure of YZS were investigated. The ET mechanism from Ce3+ to Tb3+ was also discussed in detail. The color of emitted light can be adjusted from blue to green by introducing Tb3+ ions into YZS:Ce3+. More importantly, the Tb3+ emissions under near-UV excitation are enhanced evidently, and the excitation spectrum for the Ce3+,Tb3+ co-doped phosphor matches well with the emission of near-UV chip. The selected green phosphor and commercial red, blue phosphors were coated on a 365-nm chip to fabricate a WLED device. The WLED shows an outstanding performance (R a = 93.5 and CCT = 4769 K), indicating that YZS:Ce3+,Tb3+ phosphors have potential applications in near-UV pc-WLED as a green-emitting component. • The relationship on Ce3 + luminescence and crystal structure of host. • Tb3 + emission is enhanced by energy transfer strategy. • An outstanding performance of WLED device is obtained. • YZS:Ce3 + ,Tb3 + has application in WLED as a green-emitting component. [ABSTRACT FROM AUTHOR]

A series of Ce3+ and/or Eu2+ doped T-phase orthosilicate Ba 1.2 Ca 0.8 SiO 4 (BCS) phosphors were synthesized by conventional solid state reaction. The as-synthesized samples were investigated by X-ray diffraction (XRD), photoluminescence spectroscopy, and fluorescence decay curve. The red shifts of emission peak were observed in Ce3+ and/or Eu2+ doped BCS phosphors. The possible rationalization for the red shift was discussed. The emission color for BCS:Ce3+, Eu2+ phosphors can be turned from deep blue to bluish green by varying Eu2+ concentration. The efficient energy transfer from Ce3+ to Eu2+ is responsible for this phenomenon. The energy transfer mechanism was validated and demonstrated to be a resonant type via a dipole–dipole interaction by using Inokuti–Hirayama model and Dexter's energy transfer theory. In addition, the thermal stability of the phosphors is also investigated. Furthermore, the quantum efficiency (QE) of Ba 1.15 Ca 0.8 SiO 4 :0.02Ce3+, 0.02Na+, 0.01Eu2+ phosphor was found to be 38.77%. Finally, to explore the practical applications of obtained compounds for indoor illumination, a white light-emitting-diode (LED) device which contained a n-UV chip, prepared phosphors, and green emitting and red emitting phosphors was packaged. The packaged white LEDs device can emit dazzling white light with satisfied color coordinate of (0.350, 0.335), R a (84), and correlated color temperature (4744 K). • Ce3+ and/or Eu2+ doped T-phase Ba1.2Ca0.8SiO4 phosphors were synthesized. • Efficiently energy transfer from Ce3+ to Eu2+ is confirmed. • Color tunable emissions from deep blue to bluish green are achieved. • T-phase Ba 1.2 Ca 0.8 SiO 4 :Ce3+,Eu2+ is a candidate phosphor for white LEDs. [ABSTRACT FROM AUTHOR]

Development of rare-earth-free phosphors is quite significant. It is well known that luminescence of Sn2+ depends strongly on the structure of the host crystal. The emission of Mn2+ is often very weak due to forbidden 4T 1 → 6A 1 transition. However, it can be enhanced by means of energy transfer. This work deals with the photoluminescence of calcite- and vaterite-type CaCO 3 doped with Sn2+, Mn2+ phosphors. The phosphor particles were prepared via a simple co-precipitation method. The phase purity of the synthesized particles was determined by X-ray powder diffraction. Scanning electron microscopy images were obtained to study the particle morphology. Photoluminescence properties were determined by recording the emission spectra and excitation spectra. Furthermore, the fluorescence lifetimes were recorded to investigate decay and energy transfer behavior of the samples. The emission colors of calcite-CaCO 3 :Sn2+ and vaterite-CaCO 3 :Sn2+ are different under 254 nm UV excitation, which is explained by the different coordination environment of Ca2+. For the Sn2+-Mn2+ co-doped samples, the emission intensity of Mn2+ becomes stronger than that of Mn2+ singly doped sample, which is attributed to Sn2+ → Mn2+ energy transfer. Inokuti-Hirayama model is used to analysis of the involved energy transfer mechanism. The color tone of the samples can be tuned in the visible spectral region through adjusting the Mn2+ doping concentration. Near cold white-light emission can also be achieved in a single host co-doped with Sn2+ and Mn2+. • The phosphors are rare-earth-free luminescent materials. • Stable vaterite-type CaCO 3 were prepared by a simple co-precipitation method. • PL of calcite- and vaterite-CaCO 3 :Sn2+ was studied based on crystal structure. • Mechanism of energy transfer from Sn2+ to Mn2+ was discussed. • Color tone of the samples can be tuned by changing Mn2+ concentration. [ABSTRACT FROM AUTHOR]