Synthesis and luminescence properties of CaGd2(MoO4)(4):Dy3+, Eu (3+), Tm3+ phosphors for warm white UV LEDs

A series of Dy3+, Eu3+, and Tm3+-activated CaGd2(MoO4)4 (CGM) ovoid-like microstructured phosphors have been successfully prepared using an ethylenediamine tetraacetic acid-assisted hydrothermal method at 200°C for 24 h. The crystal structure, phase, morphology, composition, and luminescence properties of the phosphors were characterized by x-ray diffraction analysis, energy-dispersive spectrometry, field-emission scanning electron microscopy, photoluminescence (PL) spectroscopy, and lifetime measurements. Under ultraviolet excitation, the rare-earth-ion activated CGM phosphors exhibited characteristic PL properties. Efficient and strong energy transfer processes from Eu3+ to Dy3+ and from Tm3+ to Dy3+ were demonstrated. The CGM:Dy3+, Eu3+, Tm3+ phosphors exhibited strong color-tunable emission and warm white light, having great potential for application in white light-emitting diodes

Synthesis and luminescence properties of CaGd2(MoO4)(4):Ln(3+) (Ln = Eu3+, Tb3+, Dy3+ and Sm3+) phosphors

The uniform monodisperse rectangular-like rare-earth-activated CaGd2(MoO4)4:Ln3+ (Ln?=?Eu3+, Tb3+, Dy3+ and Sm3+) phosphors have been synthesized by conventional solid state reaction method. The prepared phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and photoluminescence (PL) spectroscopy measurements. The XRD and FTIR results showed a scheelite-type tetragonal structure for the prepared powder samples. FTIR spectra exhibited a high absorption band situated at around 846?cm-1, which was ascribed to the Mo–O antisymmetric stretching vibrations into the [MoO4]2- tetrahedron groups and the SEM image reveals particle size in the range of 120–160?nm. The excitation/emission spectra and life times were measured to characterize the luminescent properties of the phosphors. All properties show that CaGd2(MoO4)4:Ln3+ (Ln?=?Eu3+, Tb3+,Dy3+ and Sm3+) compounds are a very appropriate red, green, yellow and orange-red emitting light–emitting phosphors promising for lighting applications

Sol-gel synthesis and luminescence properties of CaGd2(MoO4)4:Pr3+ phosphors for white LED applications

A series of novel red emitting CaGd2(MoO4)4:xPr3+ (x = 0.005–0.045) micro phosphors were successfully prepared via a simple citrate assisted sol–gel method-ray powder diffraction, scanning electron microscope, photoluminescence spectra and decay life time measurement were utilized to study the properties of CaGd2(MoO4)4:xPr3+ phosphors well crystallized, fine and homogenous micro particles appeared at the heat treatment at 900 °C for 6 h. The results confirms that CaGd2(MoO4)4 host has tetragonally distorted scheelite structure with space group I41/a. Under the excitation wavelength of 449 nm Pr3+ activated CaGd2(MoO4)4 phosphor shows the red emission peaked at about 649 nm, which is attributed to 3P0–3F2 transition of Pr3+ ions. The CIE co-ordinates of CaGd2(MoO4)4:0.035Pr3+ phosphor are x = 0.702 and y = 0.289, which are evidently close to the standard NSTC value. The luminescence properties of as prepared phosphors indicates that CaGd2(MoO4)4:xPr3+ phosphor may be a potential red emitting material for W-LED applications

Hydrothermal synthesis, characterization and luminescence properties of CaGd2(MoO4)(4):Eu3+ ovoid like structures

Tetragonal phase CaGd2(MoO4)4:Eu3+ with ovoid like hierarchical structures were prepared via employing ethylene diamine tetra acetic acid (EDTA) using the hydrothermal route at 200 °C for 24 h. X-ray diffraction patterns and field emission scanning microscopy images were used to characterize the crystal structure, phase, morphology and size of the nano samples. X-ray photo electron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (Edax) confirmed the presence of elements in phosphor samples. The PL properties of the phosphors were studied thoroughly. The photophysical properties of the samples were examined by the Judd–Ofelt theory. The CIE coordinates of the prepared phosphor samples illustrate that red light emission can be realized from CaGd2(MoO4)4:Eu3+ phosphor and it coexists very close to NTSC standard values. All these results show that ovoid like CaGd2(MoO4)4:Eu3+ micro/nanophosphor is a promising material for display applications

Synthesis, luminescent properties and energy transfer in Tb3+ and Eu3+ co-doped Li3Ba2Gd3 (MoO4)(8) phosphors for W-LED's

For the first time, single phase monoclinic Li3Ba2Gd3 (MoO4)8: 0.08 Tb3+,yEu3+ (0, 0.005, 0.02, 0.04, 0.06, 0.08 and 0.10 mol) nano phosphors were prepared by the simple mechanochemically assisted direct solid state reaction method at room temperature. Their crystal structures, luminescence properties, energy transfer mechanism and life time were studied in detail. At the excitation wavelength of 378 nm, the emission spectra of Li3Ba2Gd3 (MoO4)8: 0.08 Tb3+,yEu3+ (0, 0.005, 0.02, 0.04, 0.06, 0.08 and 0.10 mol) phosphors exhibit the characteristic emissions of Tb3+ and Eu3+ ions at around 545, 594 and 615 nm due to energy transfer from Tb3+ ions to Eu3+ ions. It is confirmed from the results that electric dipole–dipole interaction phenomena is the main cause for having energy transfer from Tb3+ to Eu3+ ions in Li3Ba2Gd3 (MoO4)8 host. The CIE coordinates of the prepared nano phosphors illustrate that by changing the ratio of Eu3+ ions the white light emission can be realized from Li3Ba2Gd3 (MoO4)8 phosphor and it coexist very close to an ideal white chromaticity coordinates (0.33, 0.33). All properties show that Li3Ba2Gd3 (MoO4)8: 0.08 Tb3+, 0.005 Eu3+ nano phosphor is a promising material for single-phase phosphor based white light emitting diodes

Enhanced Luminescence In Camoo4: Eu\u3csup\u3e3+\u3c/sup\u3e Red Phosphor Nanoparticles Prepared By Mechanochemically Assisted Solid State Meta-Thesis Reaction Method

For the first time, CaMoO4: xEu3+ (x = 0.02, 0.04, 0.06, 0.08, 0.1) red phosphor nanoparticles were synthesized using the simple mechanochemically assisted solid state meta-thesis (SSM) reaction method and the luminescence properties as a function of Eu3+ ion concentration was investigated. The characteristics of the phosphor materials were analyzed using X-ray diffraction, fourier transform infrared spectroscopy, photoluminescence (PL) and diffuse reflectance spectroscopy. For 8 mol% of Eu3+ concentration, the phosphor shows an intensified excitation peak at 392 nm indicating a strong absorption. The PL emission spectra of CaMoO4: Eu3+ phosphors showed an intense peak at 615 nm (red) which corresponds to 5D0 → 7F2 transition of Eu3+. The optimal Eu3+ concentration in CaMoO4 phosphors for enhanced red emission occurs for 8 mol% and above this concentration, the emission intensity decreases due to quenching effect. The CIE colour coordinates of the CaMoO4: 0.08Eu3+ red phosphor coincide very well with the standard values of NTSC. The red emission intensity of the SSM prepared CaMoO4: 0.08Eu3+ red phosphor is 4.7 times greater than that of the commercial Y 2O2S: Eu3+ red phosphor and 1.6 times more than the same phosphor prepared by the solid state reaction method. © 2013 Springer Science+Business Media New York