Tunable emission,energy transfer and charge compensation in SrMoO4:Sm3+,Tb3+,Na+ phosphor

A series of SrMoO₄:Sm³⁺,Tb³⁺,Na⁺ phosphors was synthesized using a high‐temperature solid‐state reaction method in air. On excitation at 290 nm, SrMoO₄:Sm³⁺,Tb³⁺ phosphor emitted light that varied systematically from green to reddish‐orange on changing the Sm³⁺ and Tb³⁺ ion concentrations. The emission intensities of SrMoO₄:Sm³⁺ and SrMoO₄:Sm³⁺,Tb³⁺ phosphors were increased two to four times due to charge compensation when Na⁺ was added as a charge compensator. The luminescence mechanism and energy transfer could be explained using energy‐level diagrams of the MoO₄^2– group, Sm³⁺ and Tb³⁺ ions. SrMoO₄:Sm³⁺,Tb³⁺,Na⁺ could be used as reddish‐orange phosphor in white light‐emitting diodes (LEDs) based on an ~ 405 nm near‐UV LED chip. This research is helpful in adjusting and improving the luminescence properties of other phosphors. Copyright © 2015 John Wiley & Sons, Ltd.     

Impact of ligand environment on optical,luminescence and thermometric behavior of A3(PO4)2:Sm3+ (A = Ca,Sr) phosphors

The present study investigates the impact of the ligand environment on the luminescence and thermometric behavior of Sm³⁺ doped A₃(PO₄)₂ (A = Sr, Ca) phosphors prepared by combustion synthesis. The structural and luminescent properties of Sm³⁺ ions in the phosphate lattices were investigated using powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques. PXRD results of the synthesized phosphors exhibit the expected phases that are in agreement with their respective standards. Fourier-transform infrared (FTIR) spectroscopy confirms the presence of PO₄ vibrational bands. Upon excitation with near ultraviolet light, the PL studies indicated that Sr₃(PO₄)₂:Sm³⁺ phosphors exhibit a yellow light emission, whereas Ca₃(PO₄)₂:Sm³⁺ phosphors exhibit an emission of orange light. The PL emission results are in accordance with the CIE coordinates, with the Sr₃(PO₄)₂:Sm³⁺ phosphors showing coordinates of (0.56, 0.44), and the Ca₃(PO₄)₂:Sm³⁺ phosphors displaying coordinates of (0.60, 0.40). Thermal analysis shows improved stability of Ca₃(PO₄)₂:Sm³⁺ based on lower weight reduction in thermogravimetric analysis. The effect of temperature on the luminescence properties of the phosphor has been examined upon a 405 nm excitation. By using the fluorescence intensity ratio (FIR) method, the temperature responses of the emission ratios from the Sm³⁺: the ⁴F_3/2 → ⁶H_5/2 transition to the ⁴G_5/2 → ⁶H_7/2 and ⁴F_3/2 → ⁶H_5/2 transition to the ⁴G_5/2 → ⁶H_9/2 emissions are characterized. The Ca₃(PO₄)₂:Sm³⁺ phosphors are more sensitive as compared with the Sr₃(PO₄)₂:Sm³⁺ phosphors. The earlier research findings strongly indicate that these phosphors hold great promise as ideal candidates for applications in non-invasive optical thermometry and solid-state lighting devices.     

Photoluminescence properties of a new orange–red‐emitting Sm3+–La3SbO7 phosphor

The antimonate compound La₃SbO₇ has high chemical stability, lattice stiffness and thermal stability. Orange–red‐emitting antimonate‐based phosphors La₃SbO₇:xSm³⁺ (x = 0.02, 0.05, 0.08, 0.10, 0.15, 0.20 and 0.25) were synthesized. The phase structure and photoluminescence properties of these phosphors were investigated. The emission spectrum obtained on excitation at 407 nm contained exclusively the characteristic emissions of Sm³⁺ at 568, 608, 654 and 716 nm, which correspond to the transitions from ⁴G_5/2 to ⁶H_5/2, ⁶H_7/2, ⁶H_9/2 and ⁶H_11/2 of Sm³⁺, respectively. The strongest emission was located at 608 nm due to the ⁴G_5/2→⁶H_7/2 transition of Sm³⁺, generating bright orange–red light. The critical quenching concentration of Sm³⁺ in La₃SbO₇:Sm³⁺ phosphor was determined as 10% and the energy transfer between Sm³⁺ was found to be through an exchange interaction. The International Commission on Illumination chromaticity coordinates of the La₃SbO₇:0.10Sm³⁺ phosphors are located in the orange–red region. The La₃SbO₇:Sm³⁺ phosphors may be potentially used as red phosphors for white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Tunable photoluminescence properties of Sr1‐yCayMoO4:Sm3+ phosphors (0 ≤ y < 1)

A series of Sr_1‐x‐yCa_yMoO₄:xSm³⁺ (0 ≤ x ≤ 7 mol% and 0 ≤ y < 1) phosphors was synthesized by a conventional solid‐state reaction method in air, and their structural and spectroscopic properties were investigated. The optimal doping concentration of Sm³⁺ in SrMoO₄:Sm³⁺ phosphor is 5 mol%. Under excitation with 275 nm, in Sr_1‐x‐yCa_yMoO₄:xSm³⁺ (0 ≤ x ≤ 7 mol% and 0 ≤ y < 1) phosphors, the emission band of the host was found to overlap with the excitation bands peaking at ~500 nm of Sm³⁺ ion, and the energy transfer from MoO₄^2? group to Sm³⁺ ion can also be observed. The International Commission on Illumination (CIE) chromaticity coordinates of Sr_0.95‐yCa_yMoO₄:0.05Sm³⁺ phosphors with excitation 275 nm varied systematically from an orange (0.4961, 0.3761) (y = 0) to a white color (0.33, 0.3442) (y = 0.95) with increasing calcium oxide (CaO) concentration. However, Sr_0.95‐yCa_yMoO₄:0.05Sm³⁺ phosphors with excitation at 404 nm only showed red emission and the energy transfer between MoO₄^2? group to Sm³⁺ ion was not observed. The complex mechanisms of luminescence and energy transfer are discussed by energy level diagrams of MoO₄^2? group and Sm³⁺ ion. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and luminescence properties of CaSnO3:Bi3+ blue phosphor and the emission improvement by Li+ ion

CaSnO₃:Bi³⁺ blue‐emitting phosphor was synthesized using a high‐temperature solid‐state reaction method in air. The crystal structures and luminescence properties were investigated. A broad emission band peaking at ~448 nm upon excitation at 262 and 308 nm was observed in the range 330–680 nm at room temperature due to ³P₁ → ¹S₀ transition of the Bi³⁺ ion. The chromaticity coordinate was (0.1786, 0.1665). The optimal Bi³⁺ ion concentration was ~0.6 mol% in CaSnO₃:Bi³⁺ phosphor. The emission spectrum of CaSnO₃:Bi³⁺ phosphor showed a blue‐shift with increasing temperature from 50 to 300 K due to the influence of temperature on the electron transition of the Bi³⁺ ion. The emission intensity of CaSnO₃:Bi³⁺ phosphor may be increased ~1.45 times by co‐doping Li⁺ ions as a charge compensator and fluxing agent. The luminescence mechanism is explained by a configurational coordinate diagram of Bi³⁺ ion in CaSnO₃:Bi³⁺ phosphor.     

Structural,morphological, and photoluminescence properties of RE (RE = Dy3+, Eu3+, Sm3+)-doped CaAlBO4 phosphor synthesized by combustion method

The CaAlBO₄:RE (RE = Dy³⁺, Eu³⁺, Sm³⁺) phosphor were prepared via combustion synthesis and studied by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectra and CIE coordinates. The phase formation of the obtained phosphor was analyzed by XRD and the result was confirmed by standard PDF Card No. 1539083. XRD data successfully indicated pure phase of CaAlBO₄ phosphor. The crystal structure of CaAlBO₄ phosphor is orthorhombic with space group Ccc2 (37). The SEM image of CaAlBO₄ phosphor reveals an agglomerated morphology and non-uniform particle size. The EDS image provides evidence of the elements present and the chemical makeup of the materials. Under the 350 nm excitation, the emission spectrum of Dy³⁺ activated CaAlBO₄ phosphor consists of two main groups of characteristic peaks located at 484 and 577 nm which are ascribed to ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transition of Dy³⁺ respectively. The PL emission spectra of CaAlBO₄:Eu³⁺ phosphor shows characteristics bands observed around 591 and 613 nm, which corresponds to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transition of Eu³⁺ respectively, upon 395 nm excitation wavelength. The emission spectra of Sm³⁺ activated CaAlBO₄ phosphor shows three characteristic bands observed at 565, 601 and 648 nm which emits yellow, orange and red color. The prominent emission peak at the wavelength 601 nm, which is attributed to ⁴G_5/2 → ⁶H_7/2 transition, displays an orange emission. The CIE color coordinates of CaAlBO₄:RE (RE = Dy³⁺, Eu³⁺, Sm³⁺) phosphor are calculated to be (0.631, 0.368), (0.674, 0.325) and (0.073, 0.185). As per the obtained results, CaAlBO₄:RE (RE = Dy³⁺, Eu³⁺, Sm³⁺) phosphor may be applicable in eco-friendly lightning technology.     

Intense green‐, red‐emitting Tb3+, Tb3+/Bi3+‐doped and Sm3+, Sm3+/La3+‐doped Ca2Al2SiO7 phosphors

This paper focuses on an optical study of a Tb³⁺/Bi³⁺‐doped and Sm³⁺/La³⁺‐ doped Ca₂Al₂SiO₇ phosphor synthesized using combustion methods. Here, Ca₂Al₂SiO₇:Sm³⁺ showed a red emission band under visible light excitation but, when it co‐doped with La³⁺ ions, the emission intensity was further enhanced. Ca₂Al₂SiO₇:Tb³⁺ shows the characteristic green emission band under near‐ultraviolet light excitation wavelengths, co‐doping with Bi³⁺ ions produced enhanced photoluminescence intensity with better colour tunable properties. The phosphor exhibited better phase purity and crystallinity, confirmed by X‐ray diffraction. Binding energies of Ca(2p), Al(2p), Si(2p), O(1s) were studied using X‐ray photoelectron spectroscopy. The reported phosphor may be a promising visible light excited red phosphor for light‐emitting diodes and energy conversion devices.     

Enhanced orange–red emission of SrZn2(PO4)2:Sm3+ via codoping Eu2+ as a sensitizer

A series of Eu²⁺‐, Sm³⁺‐ and Eu²⁺/Sm³⁺‐doped SrZn₂(PO₄)₂ samples were synthesized using a solid‐state reaction. SrZn₂(PO₄)₂:Eu²⁺ presented a broad emission band due to 4f⁶5d–4f⁷ transition of the Eu²⁺ ion. The spectra of SrZn₂(PO₄)₂:Sm sintered in air and H₂/N₂ were identical in every aspect, except for a very small difference in intensity. A Eu²⁺–Sm³⁺ energy transfer scheme was proposed to realize the sensitization of Sm³⁺ ion emission by Eu²⁺ ions, and UV‐convertible Sm³⁺‐activated red phosphor was obtained in SrZn₂(PO₄)₂:Eu²⁺, Sm³⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence properties of Sm3+‐doped YAl3(BO3)4 phosphor

A near ultraviolet excitable phosphor based on Sm³⁺‐doped YAl₃(BO₃)₄ has been synthesized by modified solid‐state reaction at 1000°C. The phase purity and photoluminescence (PL) behavior of the phosphor are studied in detail using the powder X‐ray diffraction technique and PL measurements. X‐ray diffraction reveals that the phase purity of YAl₃(BO₃)₄ critically depends upon the boric acid concentration. The phosphor has strong excitation at 406 nm in the near ultraviolet region (350–420 nm) and its emission peaks were monitored at 564, 599 and 643 nm. Further, detailed PL analysis demonstrates that the substitution of Sm³⁺ ions at sites of Y³⁺ and Al³⁺ ions enhances the PL efficiency of the phosphor appreciably. First, the PL efficiency of YAl₃(BO₃)₄:Sm³⁺ was compared with commercial (Y,Gd)BO₃:Eu³⁺ red phosphor. The Fourier transform infrared study provides essential information regarding the change in metal–oxygen bond vibrations of the phosphor. The morphology of the phosphor was investigated through scanning electron microscopy, which reveals that the phosphor possessed distorted spherical and rectangular shapes with average grain sizes in the range 0.5–1 µm. Copyright © 2013 John Wiley & Sons, Ltd.     

Multi-color luminescence of Sm3+-doped Na2YMg2V3O12 phosphor potentially applicable in white-LEDs

A novel multi-color emitting Na₂YMg₂V₃O₁₂:Sm³⁺ phosphor was synthesized using a solid-state reaction, and its crystal structure, luminescence properties, and thermal stability were studied. Charge transfer within the (VO₄)³⁻ groups in the Na₂YMg₂V₃O₁₂ host led to a broad emission band between 400 and 700 nm, with a maximum at 530 nm. The Na₂Y_1−xMg₂V₃O₁₂:xSm³⁺ phosphors exhibited a multi-color emission band under 365 nm near-ultraviolet (near-UV) light, consisting of the green emission of the (VO₄)³⁻ groups and sharp emission peaks at 570 nm (yellow), 618 nm (orange), 657 nm (red), and 714 nm (deep red) of Sm³⁺ ions. The optimal doping concentration of Sm³⁺ ions was found to be 0.05 mol%, and the dipole–dipole (d–d) interaction was primarily responsible for the concentration quenching phenomenon. Using the acquired Na₂YMg₂V₃O₁₂:Sm³⁺ phosphors, commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor, and a near-UV light-emitting diode (LED) chip, a white-LED lamp was designed and packaged. It produced bright neutral white light, manifesting a CIE coordinate of (0.314, 0.373), a color rendering index (CRI) of 84.9, and a correlated color temperature (CCT) of 6377 K. These findings indicate the potential of Na₂YMg₂V₃O₁₂:Sm³⁺ phosphor to be used as a multi-color component for solid-state illumination.     

Synthesis and photoluminescence characteristics of Sm3+‐doped Bi4Si3O12 red‐emitting phosphor

A series of novel red‐emitting Sm³⁺‐doped bismuth silicate phosphors, Bi₄Si₃O₁₂:xSm³⁺ (0.01 ≤ x ≤ 0.06), were prepared via the sol–gel route. The phase of the synthesized samples calcinated at 800 °C is isostructural with Bi₄Si₃O₁₂ according to X‐ray diffraction results. Under excitation with 405 nm light, some typical peaks of Sm³⁺ ions centered at 566, 609, 655 and 715 nm are found in the emission spectra of the Sm³⁺‐doped Bi₄Si₃O₁₂ phosphors. The strongest peak located at 609 nm is due to ⁴G_5/2–⁶H_7/2 transition of Sm³⁺. The luminescence intensity reaches its maximum value when the Sm³⁺ ion content is 4 mol%. The results suggest that Bi₄Si₃O₁₂:Sm³⁺ may be a potential red phosphor for white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermally stable Sm3+-doped alkali zinc alumino borosilicate (AZABS) glass for warm white light generation and w-LED applications

Samarium ion (Sm³⁺)-doped alkali zinc alumino borosilicate (AZABS) glass was synthesized via quick melt quench technique. Various spectroscopic studies like optical absorption, photoluminescence (PL) emission, PL excitation, temperature-dependent PL and PL decay kinetics were performed on the as prepared glass system. Under 402 nm excitation, three sharp bands at wavelengths 563, 599 and 645 nm corresponding to transitions ⁴G_5/2 → ⁶H_5/2, ⁶H_7/2 and ⁶H_9/2, respectively, can be seen in the PL emission spectra. The 0.25 mol% Sm³⁺ glass has the highest intensity for these emissions. The lanthanide interaction in the glass matrix is dipole–dipole in nature as was proven from Dexter's analysis. The direct bandgap of 0.25 mol% Sm³⁺-doped AZABS glass was calculated to be 2.88 eV. The lifetimes of the as prepared glass range from 1.93 ms for the lowest concentration of Sm³⁺ to 0.75 ms for the highest. From temperature dependent PL studies, the activation energy for 0.25 mol% Sm³⁺-doped AZABS glass was found to be 0.19 eV which shows high thermal stability of this glass. We propose to utilize these Sm³⁺-doped AZABS glasses for white-light emitting diodes (w-LEDs) and solid-state lighting (SSL) applications.     

Emission analysis of Tb3+‐and Sm3+‐ion‐doped (Li2O/Na2O/K2O) and (Li2O + Na2O/Li2O + K2O/K2O + Na2O)‐modified borosilicate glasses

Four series of borosilicate glasses modified by alkali oxides and doped with Tb³⁺ and Sm³⁺ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B₂O₃ + 10SiO₂ + 5MgO + R + 0.5(Tb₂O₃/Sm₂O₃) [where R = 10(Li₂O /Na₂O/K₂O) for series A and C, and R = 5(Li₂O + Na₂O/Li₂O + K₂O/K₂O + Na₂O) for series B and D]. The X‐ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the ⁵D₄ → ⁷F₅ (543 nm) transition of the Tb³⁺ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm³⁺ ions with the series C and D glasses showed strong reddish‐orange emission at 600 nm (⁴G_5/2 →⁶H_7/2) with an excitation wavelength λ_exci = 404 nm (⁶H_5/2→⁴F_7/2). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb³⁺ and Sm³⁺ ions was studied to optimize the potential alkali‐oxide‐modified borosilicate glass.     

Structural and luminescence properties of Sm3+‐doped bismuth phosphate glass for orange‐red photonic applications

In the present study, the effect of bismuth oxide (Bi₂O₃) content on the structural and optical properties of 0.5Sm³⁺‐doped phosphate glass and the effect of concentration on structural and optical properties of Sm³⁺‐doped bismuth phosphate (BiP) glass were studied. Structural characterization was accomplished using X‐ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and ³¹P nuclear magnetic resonance (NMR) spectroscopy. Optical properties were studied using absorption, photoluminescence and decay measurements. Using optical absorption spectra, Judd–Ofelt parameters were derived to determine the local structure and bonding in the vicinity of Sm³⁺ ions. The emission spectra of Sm³⁺‐doped BiP glass showed two intense emission bands, ⁴G_5/2→⁶H_7/2 (orange) and ⁴G_5/2→⁶H_9/2 (red) for which the stimulated emission cross‐sections (σ_e) and branching ratios (β) were found to be higher. The quantum efficiencies were also calculated from decay measurements recorded for the ⁴G_5/2 level of Sm³⁺ ions. The suitable combination of Bi₂O₃ (10 mol%) and Sm³⁺ (0.5 mol%) ions in these glasses acted as an efficient lasing material and might be suitable for the development of visible orange‐red photonic materials.     

Influence of rare earth elements (Y,Gd and Lu) on the luminescent properties of green phosphor ZnMoO4:Tb3+

(Zn,Ln_x)MoO₄:Tb³⁺ (Ln = Y³⁺, Gd³⁺ and Lu³⁺) were prepared using the co‐precipitation method. Phase impurity, morphology and composition were investigated by power X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The experimental results show that crystal structure is not destroyed after doping an appropriate amount of Y³⁺, Gd³⁺ and Lu³⁺. EDS analysis reveals that Y, Gd and Lu have been successfully doped into ZnMoO₄. In addition, the morphology of the phosphors is notably improved, exhibiting homogeneous dispersion morphology and irregular shapes of particle size ~ 0.5–1 µm. The luminescent intensity of (Zn,Ln_x)MoO₄:Tb³⁺ (Ln = Y³⁺, Gd³⁺ and Lu³⁺) phosphor is obviously higher than that of ZnMoO₄:Tb³⁺ phosphor. The energy transfer process between trivalent rare earth ions indicates that the inert earth ions can act as an energy bridge from MoO₄^2‐ to Tb³⁺. Copyright © 2013 John Wiley & Sons, Ltd.     

Luminescence in Li3Al2(PO4)3:Eu2+

A series of efficient Li₃Al₂(PO₄)₃:Eu²⁺ novel phosphors were synthesized by the facile combustion method. The effects of dopant on the luminescence behavior of Li₃Al₂(PO₄)₃ phosphor were also investigated. The phosphors were characterized by X‐ray diffraction, field emission scanning electron microscope and photoluminescence techniques. The result shows that all samples can be excited efficiently by near‐ultraviolet excitation under 310 nm. The emission was observed for Li₃Al₂(PO₄)₃:Eu²⁺ phosphor at 425 nm, which corresponded to the d → f transition. The concentration quenching of Eu²⁺ was observed in Li₃Al₂(PO₄)₃:Eu²⁺ when the Eu concentration was at 0.5 mol%. The prepared powders exhibited intense blue emission at the 425 nm owing to the Eu²⁺ ion by Hg‐free excitation at 310 nm (i.e., solid‐state lighting excitation). Consequently, the availability of such a phosphor will significantly help in the development of blue‐emitting solid‐state lighting applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Bi3+ addition on the upconversion luminescence properties of NaYbF4:Er

In this study, Bi³⁺ incorporation in NaYbF₄:Er lattice and its influence on upconversion luminescence properties have been investigated in detail using techniques such as temperature‐dependent luminescence, Fourier transform infrared spectroscopy and X‐ray diffraction (XRD). The study was carried out to develop phosphors with improved upconversion luminescence. From photoluminescence and lifetime measurements it is inferred that luminescence intensity from NaYbF₄:Er increases with Bi³⁺ addition. The sample containing 50 at.% Bi³⁺ ions exhibited optimum upconversion luminescence. Increased distance between Yb³⁺–Yb³⁺ and Er³⁺–Er³⁺ due to Bi³⁺ incorporation into the lattice and associated decrease in the extent of dipolar interaction/self‐quenching are responsible for increase in lifetime values and luminescence intensities from Er³⁺ ions. Incorporation of Bi³⁺ into NaYbF₄:Er lattice reduced self‐quenching among Yb³⁺–Yb³⁺ions and this facilitated energy transfer from Yb³⁺ to Er³⁺. This situation also explains decrease in the extent of temperature‐assisted quenching of emission from thermally coupled ²H_11/2 and ⁴S_3/2 levels of Er³⁺. Based on Rietveld refinement of XRD patterns it was confirmed that a maximum of 10 at.% of Bi³⁺added was incorporated into the NaYbF₄:Er lattice and the remaining complex co‐exists as a BiOF phase. These results are of significant interest in the area of development of phosphors based on Yb³⁺–Er³⁺ upconversion luminescence.     

Solid‐state synthesis and luminescent properties of yellow‐emitting phosphor NaY(MoO4)2:Dy3+ for white light‐emitting diodes

A yellow‐emitting phosphor NaY(MoO₄)₂:Dy³⁺ was synthesized using a solid‐state reaction at 550 °C for 4 h, and its luminescent properties were investigated. Its phase formation was studied using X‐ray powder diffraction analysis, and there were no crystalline phases other than NaY(MoO₄)₂. NaY(MoO₄)₂:Dy³⁺ produced yellow emission under 386 or 453 nm excitation, and the prominent luminescence was yellow (575 nm) due to the ⁴ F_9/2→⁶H_13/2 transition of Dy³⁺. For the 575 nm emission, the excitation spectrum had one broad band and some narrow peaks; the peaks were located at 290, 351, 365, 386, 426, 453 and 474 nm. Emission intensities were influenced by the Dy³⁺ doping content and a concentration quenching effect was observed; the phenomenon was also proved by the decay curves. Moreover, the Commission International de I'Eclairage chromaticity coordinates of NaY(MoO₄)₂:Dy³⁺ showed similar values at different Dy³⁺ concentrations, and were located in the yellow region. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel red emitting phosphor LiBaB9O15:Sm2+/Sm3+, li+ with broad excitation band for white LEDs

A novel tunable red emitting phosphor LiBaB₉O₁₅:Sm²⁺/Sm³⁺, Li⁺ with broad excitation band was synthesized by a high temperature solid‐state method. Luminescence properties were investigated in detail by luminescence, X‐ray photoelectron spectroscopy (XPS) spectra and CIE chromaticity coordinates. XPS data confirmed that there were Sm³⁺ in LiBaB₉O₁₅:Sm³⁺ and Sm²⁺/Sm³⁺ in LiBaB₉O₁₅:Sm²⁺/Sm³⁺, respectively. Spectral property of LiBaB₉O₁₅:Sm³⁺, LiBaB₉O₁₅:Sm³⁺/Sm²⁺ and LiBaB₉O₁₅:Sm²⁺, Li⁺ presented that the excitation band of Sm³⁺ widened and the excitation band of Sm²⁺ ranged from 350 to 450 nm. And the red light color is tunable with changing Li⁺ concentration. The results indicated that LiBaB₉O₁₅:Sm²⁺/Sm³⁺, Li⁺ may be promising red phosphor for white light emitting diodes.     

Study of luminescence and effect of Dy3+ on NaMgSO4Cl:Ce chlorosulphate phosphor

Chlorosulphate NaMgSO₄Cl phosphor doped with Ce³⁺ and co‐doped by Dy³⁺ prepared by the wet chemical method was studied for its photoluminescence and thermoluminescence (TL) characteristics. The emission spectrum of Ce³⁺ shows dominant peaks at 346 nm (excitation 270 nm) due to 5d → 4f transition. Efficient energy transfer occurs from Ce³⁺ → Dy³⁺ ions. Dy³⁺ emission at 485 nm and 576 nm is due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ion respectively. The TL glow curves of NaMgSO₄Cl:Ce and Ce,Dy have been recorded for various concentrations at a heating rate of 2 °C/s irradiated by γ‐rays at a dose rate of 0.995 kGy/h for 1 Gy, which peaks at about 241 °C and 247‐312 °C respectively. Further, in changing the concentration level, the general structure of the intensity is found to increase. The main property of this phosphor is its sensitivity even for low concentrations of rare earth ions and low γ‐ray dose. There is still scope for higher doses of γ‐radiation. The phosphor presented may be used as a lamp phosphor as well as for TL studies. Copyright © 2014 John Wiley & Sons, Ltd.