Photoluminescence properties of KSrPO4:Sm3+ phosphor for SSL applications (original) (raw)
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Journal of the American Chemical Society, 2010
The orthophosphate host family, A I B II PO 4 (A I) monovalent cation, B II) divalent cation), has recently been made available as phosphors that combine with near-UV lighting chips for use in solid-state white light-emitting diodes (LEDs). This study elucidates the crystalline structure and lattice parameters of the products via a solid-state reaction, using powder X-ray diffraction (XRD) and GSAS refinement. The versatility of the phosphor host A I B II PO 4 is established by examining isovalent substitutions of four cations in the structuresLi or K for A I , Sr or Ba for B II sand three doped activators, RE) Eu 2+ , Tb 3+ , and Sm 3+. The luminescence properties, decay time, and Commission Internationale de l'É clairage (CIE) chromaticity index are determined for various concentrations of these activators and metal constituents of the host. The thermal stabilities of all of these compounds are determined for the first time from the crystal structure and the coordination environment of the rare-earth metal. The morphology, composition, and particle size were measured in detail. Finally, density functional calculations were performed using the generalized gradient approximation plus an on-site Coulombic interaction correction (GGA+U) scheme to investigate the electronic structures of the KSrPO 4 system. A concise model was proposed to explain the luminescence mechanism.
Recent progress in phosphate based luminescent materials: A case study
Journal of Physics: Conference Series, 2021
The uses of phosphate based luminescent materials are presented in this study in different fields of luminescence. There are different types of luminescent phosphors are available in the field of luminescence such as borates, sulphates, fluorides, sulphides, phosphates etc. From all these phosphors, phosphate-based phosphors shows their potential in almost every field of luminescence in last few years and it becomes a key material in the luminescence especially in photoluminescence, thermoluminescence and mechanoluminescence. These rare earths activated phosphate-based luminescence materials are synthesized with different techniques by means of wet chemical method, combustion technique, sol gel analysis and solid-state diffusion technique etc. which are described in the present article. Consequently, this article chiefly dealing the overview of different phosphate based luminescent materials and modern development and progression in the field of luminescence.
New square-planar complexes [Pt(1 −H ) 2 ] (2a) [1 −H = (oxazolin-2-yl)bis(diphenylphosphino)methanide] and [Pd(1 −H ) 2 ] (2b), of general formula [M{(Ph 2 P) 2 C---C---NCH 2 CH 2 O} 2 ] (M = Pt, 2a; M = Pd, 2b), result from deprotonation of 2-{bis(diphenylphosphino)methyl}oxazoline (1) at the PCHP site. The new, functionalized dppm-type ligand 4-{bis(diphenylphosphino)methyl}pyridine, (Ph 2 P) 2 CH(4-C 5 H 4 N) (4), was prepared by double lithiation and phosphorylation of 4-picoline. In the presence of NEt 3 , the reactions of 2 equiv of 4 with [PtCl 2 (NCPh) 2 ] and [Pd(acac) 2 ] (acac = acetylacetonate) afforded [Pt(4 −H ) 2 ] (5a) [4 −H = bis(diphenylphosphino)(pyridin-4-yl)methanide] and [Pd(4 −H ) 2 ] (5b), of general formula [M{(Ph 2 P) 2 C(4-C 5 H 4 N)} 2 ] (M = Pt, 5a; M = Pd, 5b), respectively.
A series of Pr 3þ activated alkaline-sodium-phosphate (NaMPO 4 , where M ¼ Mg, Ca, Sr and Ba) phosphors were prepared by conventional solution combustion method with the fixed doping concentration of Pr 3þ (1.0 mol%). The crystal phase formation and morphology of the phosphates were analyzed by X-ray powder diffraction (XRD) and field emission scanning electron microscope (FE-SEM), respectively. The optical properties including reflectance, excitation and emission and the color coordinates were investigated. The band gap of the phosphors was calculated from diffuse reflectance spectra data using the KubelkaeMunk function. The photoluminescence (PL) excitation spectra showed the excitation peaks ranging from 420 to 475 nm and emission peaks were observed in the visible region and were found to vary for different hosts. Pr 3þ -doped phosphors can display very distinct dominant red emission due to the 3 P 0 / transitions. The Pr 3þ PL emission spectrum was observed from NaMPO 4 phosphors at 605 nm. This emission under 445 nm excitation makes these materials possible candidates to serve as sources of red light in tricolor system used for solid state lighting. Different results on the luminescence features of Pr 3þ :NaMPO 4 are discussed on the basis of crystal structure. The Pr 3þ ion has structure-dependent transitions due to the special microstructures present in a given host. The results indicated that among the four different alkaline cations, Ca þ2 not only provides the most intense emission from Pr 3þ but it also produces electric-dipole dominated transition ( 3 P 0 / 3 H 5 ) resulting in the most intense reddish-orange emission.
Luminescence properties of tricalcium phosphate doped with dysprosium
Applied Radiation and Isotopes, 2020
Tricalcium phosphate having effective atomic number Z eff ¼ 15.785, equivalent to that of bones was studied for its thermoluminescence (TL) and photoluminescence (PL) properties. Different samples with varied concentrations of the dopant Dy 3þ (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mol %) were synthesized by the chemical coprecipitation technique. Phase and compound confirmations were done using X-Ray Diffraction (XRD) and the phosphors' crystallite size was calculated using Scherrer's formula which was found to range between 27 nm and 49 nm. The surface morphological study was done using Field Emission-Scanning Electron Microscopy (FE-SEM). Other characterization techniques used for compound confirmation included Energy Dispersive X-Ray Spectroscopy (EDX) and Fourier Transform Infrared Spectroscopy (FTIR). Samples were further irradiated by gamma rays (emitted from Co-60) with dose varying from 10 Gy to 5 kGy in order to study their TL properties. Concentration optimization of the given phosphor was done in terms of its TL intensity and was found to be 0.5 mol %. The TL dose response of the phosphor was linear over a wide range of dose (10 Gy-3 kGy). Deconvolution was performed on the glow curve for 10 Gy dose, giving six peaks (at 127 o , 153 o , 185 o , 218 o , 313 o and 335 o C) suggesting the presence of six different types of traps. Other characteristics of the TL material i.e. repeatability and fading were also studied. Overall, the phosphor showed promising results for its utility in TL dosimetry. In addition to the TL, PL further confirmed the presence of dopant in the phosphor. Moreover, the dopant concentration was optimized in terms of the nanophosphor's PL intensity. The Commission International de l' � Eclairage (CIE) was used to calculate chromaticity coordinates, colour rendering index and colour temperature in order to investigate the phosphor's application in white LEDs.
Journal of Alloys and Compounds, 2019
A new phosphate Ba 3 In 4 (PO 4) 6 has been discovered in the exploration of novel host materials for color-tunable phosphors in BaO-In 2 O 3-P 2 O 5 system. The crystal-structure determination using powder XRD data reveals it belongs to the cubic langbeinite structure type (S.G. P2 1 3), unlike Mg 3 In 4 (PO 4) 6 crystallizing the triclinic system (S.G. P1 ത). The existence of PO 4 has been verified by IR spectra of the title compound. DTA and experimental indicate that this new phosphate has a high melting point of ~1293 °C. Combined with calculated electronic structure and experimental UV-Vis diffuse reflectance spectrum, it has a wide direct energy band gap which is favorable for host materials. The site symmetry of Eu 3+ ions and the cross relaxation of Tb 3+ ions in this matrix have been clarified according to their luminescence properties. Red-pink-green tunable emission can be realized adjusting the Eu 3+ and Tb 3+ contents. The quantum yields of representative phosphors under the excitation of 370-392 nm ultraviolet radiation have been measured and discussed. The PL intensity of Ba 3 In 4 (PO 4) 6 : 0.02Eu 3+ , 0.015Tb 3+ phosphor at 423 K of is about 67% of that at 298 K. Present results indicate that the Ba 3 In 4 (PO 4) 6-based phosphors are valuable for the multicolor and stable thermal performance in the display and lighting fields.
NaLi2PO4:Eu3+ based novel luminescent red phosphor
Eu3? doped NaLi2PO4 red luminescent phosphor has been synthesized by solid state reaction and its phase purity has been confirmed by X-ray diffraction analysis. Optical properties of the phosphor have been investigated and the effect of dopant (Eu3?) concentration (0.1–3.0 mol%) has been observed. Excitation spectra of the phosphor NaLi2- PO4:Eu3? show a very efficient absorbance band corresponding to the common allowed transition 7F0 ? 5L6 occurring at 393 nm, while the luminescence spectra exhibit prominent emission peak centered at 702 nm (5D0 ? 7F4) in pure red region. Color purity of this red phosphor has been calculated and found to be around 99.9 %, which is very close to that of commercial red phosphor Y2O3:Eu3?. Luminescence studies of the phosphor show excellent stability with respect to excitation energy. Chromatic investigations have also been performed using emission spectrum and some important chromatic parameters are calculated using CIE-1931 color calculator in order to find potential application of the phosphor.
Indian Journal of Materials Science, 2014
The spectral properties of the K3La(PO4)2:Eu3+nanophosphors synthesized by the combustion method are reported. The phosphors were characterized by X-ray diffraction, transmission electron microscopy, and optical spectroscopy. The XRD pattern reveals a pure monoclinic phase of the K3La(PO4)2with the average particle size of 30 nm in diameter. Under UV excitation, the phosphors exhibited several emission bands which were assigned to 4f-4f transitions of Eu3+ions. The red shade of the Eu3+ion with the CIE coordinates (x,y) as (0.63, 0.37) suggests that this material is a promising phosphor for near-UV InGaN-based LED lighting.