Tm Phosphors Research Articles

The Effect of a Yb Co-Dopant on the Blue Upconversion and Thermoluminescent Emission of SrLaAlO4:Yb3+,Tm3+ Phosphors

In this study, we described the structural, morphological, optical, photoluminescence, and thermoluminescence properties of SrLaAlO4:Tm3+,Yb3+ (SLAO:Tm,Yb) blue-emitting phosphors made by combustion synthesis and a post-annealing treatment at 1200 °C. The Yb co-dopant concentration was varied (1.0, 3.0, 5.0, and 6.0 mol%) while the Tm dopant concentration was fixed at 5 mol%. According to the X-ray diffraction patterns, all the samples presented the pure tetragonal phase of SrLaAlO4. Scanning electron microscopy analysis showed that the SLAO powders had morphologies of irregular or bar grains with average sizes in the range of 0.5–1.07 µm. Photoluminescence emission under 980 nm excitation showed an intense blue emission peak at 481 nm. The phosphors also emitted red light at 654 nm and a prominent NIR emission at 801 nm. All those emissions correspond to 1G4 → 3H6, 1G4 → 3H4 and 3H4 → 3H6 transitions of Tm3+. The SLAO:Tm,Yb phosphors synthesized with 3.0 mol.% of the Yb co-dopant showed the highest emission intensity in the visible/near-infrared (NIR) range (400–800 nm), and its CIE coordinates corresponded to the blue color (0.19368, 0.15826). Additionally, thermoluminescence emissions were recorded for the SLAO:Tm,Yb phosphors. The samples were previously irradiated with UV wavelengths of 265 nm, 365 nm, and 385 nm prior to the thermoluminescent measurements. After this, the kinetic parameters such as frequency factors, activation energy (E), and order of kinetics were calculated using the Chen method. The thermoluminiscent emissions demonstrated that the SLAO:Yb,Tm phosphors can be used for UV dosimetry.

The role of chelating agent on the structure and up-conversion property of NaLuF4:Yb,Tm as security ink phosphor

Purpose This study aims to investigate the effect of trisodium nitrilotriacetic acid (NTA) on the physical and luminescence emission properties of NaLuF4:Yb, Tm Upconversion (UC) particles and compared with trisodium citrate (CA). Upconversion materials have been remarkably considered in many applications in the past decades. However, the morphology of the UC particles affects their emission properties, depending on the synthesis situation. Design/methodology/approach The UC particles were synthesized by the hydrothermal method. Properties such as crystal phase, particle morphology, particle size, smoothness and uniformity of particle surface and their emission intensity in the UV–Vis region were studied. Findings Observations showed that pH is an essential factor in determining the crystalline phase. In addition, quality factors affect the morphology, particle size and surface smoothness of crystalline facets. It was also found that the UC particles synthesized in the presence of trisodium NTA have a much higher emission intensity than those synthesized in the presence of CA. The use of UC particles in security inks to maintain the brand was also investigated. Originality/value To the best of the authors’ knowledge, for the first time, the effect of trisodium NTA as a chelating agent was investigated on morphology and UC intensity of NaLuF4:Yb,Tm phosphor.

Enhancing of the blue/NIR emission of novel BaLaAlO4:Yb3+(X mol%),Tm3+ (0.5 mol%) upconversion phosphors with the Yb3+ concentration (X = 0.5 to 6)

We report the structural, morphological and luminescent properties of the BaLaAlO4:Yb3+,Tm3+ (BAL:Yb,Tm) phosphors synthesized by a combustion method. The concentration of Tm3+ was fixed at 0.5 mol%, while that of Yb3+ was varied from 0 to 7 mol%. The X-ray diffraction patterns demonstrated that the samples synthesized with the Yb3+ co-dopant had an orthorhombic phase. In addition, the scanning electron microscopy images revealed that the BAL:Yb,Tm phosphors are formed by a mixture of coalesced microparticles with irregular shape and their surface is decorated with smaller nanoparticles. The size of these nanoparticles increases from 67 to 838 nm after increasing the Yb3+ concentration from 0 to 7 mol%. The BAL:Yb,Tm phosphors produced blue, red and Near infrared emission bands centered at 478, 658 and 800 nm (under 980 nm excitation), respectively. Moreover, the CIE (International commission on illumination) coordinates were calculated for all the samples and realized that they are always in the blue region of the CIE map. This suggests that the increase of the Yb3+ concentration in the BAL:Yb,Tm phosphors mainly favors the blue emission at 478 nm, since the red emission was always weak and contributed at most with ≈26% of the overall emission. Thus, the results of this work indicate that the BAL:Yb,Tm phosphors could be good candidates for their use in biomarkers or lighting applications.

Color modification of ZnGa2O4:Yb3+,Er3+,Tm3+ upconversion phosphors with the doping of Sn4+ and Ge4+ ions.

Upconversion phosphors Zn3Ga2SnxGe1-xO8:Yb3+,Er3+,Tm3+ were prepared by solid-state reaction with a subsequent thermal treatment at 1300°C. Under the excitation of a 980 nm laser, all phosphors produced blue emission at 477 nm, green emissions at 526 nm and 549 nm, and red emissions at 659 nm and 694 nm. The doping of Sn4+ ions and Ge4+ ions had no effect on the positions of upconversion emission peaks. However, the emission intensity changed in different degrees with different doping ions in the matrix. According to the basic theory of color-light, it is known that the color-light can be obtained by mixing a definite ratio of red, green, and blue emissions. Specifically, in the 980 nm light excitation, ZGO:Yb,Er,Tm phosphors show purplish pink luminescence, while ZGSO:Yb,Er,Tm show greenish blue luminescence, ZGGO:Yb,Er,Tm show purplish blue luminescence, and ZGGSO:Yb,Er,Tm show blue luminescence. In other words, doping Sn4+ ions can move upconversion luminescence toward the green region, while doping Ge4+ ions bend it toward the blue region. Adjusting the doping of Sn4+ ions and Ge4+ ions can obviously change the upconversion luminescent color. Besides, the upconversion luminescence of all as-prepared phosphors is visible to the naked eye without additional optical instruments.

Tunable upconversion luminescence of SrF2: Er,Tm phosphors

In preset paper, for the first time upconversion luminescence (UCL) of SrF2:Er,Tm phosphors upon excitation of 4I13/2 level of Er3+ were investigated. Fluorite-type SrF2:Er,Tm phosphors were synthesized by co-precipitation from aqueous nitrate solution technique. Tuning the UCL by SrF2:Er through Tm3+ ions co-doping was demonstrated. Also we estimated the UCL energy yield in the visible and near-infrared spectral range.

Color-tunable and upconversion luminescence of Gd2O2S:Er,Tm phosphor: experimental investigations and first-principles calculation

The Er3+, Tm3+ co-doped gadolinium oxysulfide phosphors were prepared using solid-state reaction in vacuum. The crystal structure, morphology, and photoluminescence characteristics were, respectively, investigated by X-ray diffraction, transmission electron microscope, upconversion luminescence spectra and Commission Internationale de L’Eclairage diagram. Under 980 nm excitation, the quenching concentration of Er3+ was revealed to be 7 mol% with highest luminescence intensity and fluorescence lifetime. The emitting color of Gd2O2S:Er,Tm phosphors can be tuned by adjusting the concentration of Er3+ and Tm3+. First-principles calculation was employed to clarify the luminescence mechanism of the impurities doped in gadolinium oxysulfide host lattice by calculated band structure, density of states and absorption spectrum.

A new yellow long persistent luminescence phosphor Ca2Al2SiO7:Eu2+,Tm3+ found by co-doping Ln3+ (Ln = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) with Eu2+ in Ca2Al2SiO7 host

A series of Eu2+ doped Ca2Al2SiO7 (CASO) phosphors with or without Ln3+ (Ln = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) co-dopant in the host were synthesized by solid-state reaction method in order to obtain long persistent luminescence (LPL). Their structural and photoluminescent properties were investigated by X-ray powder diffraction (XRD) and photoluminescence emission (PL) and excitation (PLE) spectra in detail. Meanwhile, the decay curve measurements were performed on those phosphors to study their afterglow properties. Among them, the Ca2Al2SiO7:Eu2+,Tm3+ (CASO:Eu,Tm) phosphor yielded a bright LPL in the yellow region with afterglow duration much longer than those of other samples. Its luminescence can be observed by human eye for more than 2 h after shutting down the 365 nm excitation source. Further thermoluminescence (TL) study on CASO:Eu,Tm phosphor indicated that the introduced Tm3+ ions indeed increased substantially the amount of charge carrier traps. A possible explanation were given to illustrate the LPL mechanism of CASO:Eu,Tm based on the experimental results. This work suggests that CASO:Eu,Tm phosphor is a promising yellow-emitting LPL phosphor.

Enhanced Up-Conversion Emission in Al3+ Co-Doped ZnGa2O4:Yb3+,Tm3+ Powder Phosphors.

Yb3+-Tm3+ co-doped up-conversion powder phosphors using Zn(AlxGa1-x)2O4 (ZAGO) as the host materials were synthesized via solid-state reaction successfully. In addition, the morphology, structural characterization and up-conversion luminescent properties were all investigated by scanning electron microscope (SEM), x-ray diffraction (XRD) and fluorescence spectrophotometer (F-7000), respectively. Under the excitation of a 980nm laser, all as-prepared powders can carry out blue emission at about 477nm (corresponding to 1G4→3H6 transition of Tm3+ ions), and red emission at about 691nm (attributed to 3F3→3H6 transition of Tm3+ ions). Also, the influence of doping Al3+ ions were investigated. In brief, the doping of Al3+ ions has no effect on the position of emission peak. Howbeit the up-conversion efficiency and intensity of ZAGO:Yb,Tm phosphors are stronger than ZGO:Yb,Tm and ZAO:Yb,Tm phosphors, while the crystallinity is the opposite. More particularly, all as-prepared powder phosphors emit strong luminescence, which is observable by the naked eye, demonstrating the potential applications in luminous paint, luminescent dye, etc.

Synthesis and Characterization of Monodisperse Core-shell Lanthanide Upconversion Nanoparticles NaYF4: Yb,Tm/SiO2

Lanthanide up-converting luminescent nanoparticles (UCNPs) are exciting and promising materials for optical bioimaging, biosensor and theranostic due to their unique and advantageous optical and chemical properties. The UCNPs absorb low energy near-infrared (NIR) light and emit high-energy shorter wavelength photons (visible light). Their unique features allow them to overcome various problems associated with conventional imaging probes such as photostability, lack of toxicity, and to provide versatility for creating nanoplatforms with both imaging and therapeutic modalities. This paper reports synthesis and characterization of core-shell structured of NaYF4:Yb,Tm/SiO2 microspheres. The synthesis of lanthanide upconversion nanoparticles NaYF4:Yb,Tm was prepared by thermal decomposition process which involves dissolving organic precursors in high-boiling-point solvents oleic acid (OA) and octadecene (ODE). After that, the NaYF4:Yb,Tm phosphors was coated by silica via reverse microemulsion process to obtain core-shell structured NaYF4:Yb,Tm/SiO2. Scanning electron microscopy, transmission electron microscopy, specific area electron diffraction, and photoluminescence were applied to characterize these samples. The obtained core-shell structured NaYF4:Yb,Tm/SiO2 phosphors exhibit a perfect cubic morphology with narrow size distribution and smooth surface. Upon IR excitation at 980 nm, the NaYF4:Yb,Tm/SiO2 samples exhibit whitish blue upconversion (UC) luminescence, respectively. These phosphors show potential applications in the displaying on biological fields and biosensing.

Surface temperature measurements from a stator vane doublet in a turbine afterburner flame using a YAG:Tm thermographic phosphor

Phosphor thermometry measurements in turbine engine environments can be difficult because of high background radiation levels. To address this challenge, luminescence lifetime-based phosphor thermometry measurements were obtained using thulium-doped Y3Al5O12 (YAG:Tm) to take advantage of the emission wavelengths at 365 nm (1D2 → 3H6 transition) and at 456 nm (1D2 → 3F4 transition). At these wavelengths, turbine engine radiation background is reduced compared with emission from longer wavelength phosphors. Temperature measurements of YAG:Tm coatings were demonstrated using decay of both the 365 and 456 nm emission bands in a furnace environment up to 1400 °C. To demonstrate that reliable surface temperatures based on short-wavelength YAG:Tm emission could be obtained from the surface of an actual engine component in a high gas velocity, highly radiative environment, measurements were obtained from a YAG:Tm-coated Honeywell stator vane doublet placed in the afterburner flame exhaust stream of the augmenter-equipped General Electric J85 turbojet test engine at the University of Tennessee Space Institute (UTSI). Using a probe designed for engine insertion, spot temperature measurements were obtained by measuring luminescence decay times over a range of steady state throttle settings as well as during an engine throttle acceleration. YAG:Tm phosphor thermometry measurements of the stator vane surface in the afterburner exhaust stream using the decay of the 456 nm emission band were successfully obtained at temperatures up to almost 1300 °C. Phosphor thermometry measurements acquired with the engine probe using the decay of the 365 nm emission band were not successful at usefully high temperatures because the probe design allowed transmission of intense unfiltered silica Raman scattering that produced photomultiplier tube saturation with extended recovery times. Recommendations are made for probe modifications that will enable temperature measurements using the 365 nm emission band decay, which will be beneficial in environments with strong reflections of combustor radiation.

Luminescence Studies on Ba Doped With Eu and Tm Phosphors

Di-barium magnesium silicate doped with Eu $^{2+}$ and Tm $^{3+}$ phosphors were prepared for different concentrations of Tm $^{3+}$ ions keeping the concentration of Eu $^{2+}$ as 0.5 mol%. Photoluminescence (PL) studies of prepared samples were carried out. Emission spectra exhibited optimum green color emission at 509 nm when Tm $^{3+}$ was 1.5 mol%. Emission is expected to arise due to the transition of Eu $^{2+}$ ions from any of the sublevels of 4d $^{6}$ 5f $^{1}$ to its ground state ( ${}^{8}$ S $_{7/2})$ . This sample with 1.5 mol% of Tm $^{3+}$ is taken for X-ray diffraction analysis. XRD pattern confirmed that the sample follows monoclinic structure with C 1 2/c 1 (15) space group. Scanning Electron Microscope image of the sample exhibited the uniform morphology with average particle size of 222.54 $\mu$ m . Thermoluminescence (TL) glow curves of the sample for different UV irradiation were also recorded which presented single broaden peak centered at about ${\hbox{91}} ^{\circ}$ C. Phosphorescence decay curve was indicative of presence of dual exponential decaying section with a fast decay followed by a long decaying part.

Improved near-infrared up-conversion emission of YAG:Yb,Tm phosphor substituted by Gallium and Indium

Gallium–Indium co-substituted yttrium aluminum garnet (YAG:Yb,Tm) phosphors were synthesized by co-precipitation method. It can be seen that gallium and indium ions co-substitution didn’t change the phase of YAG. The upconversion luminescence (UCL) properties of the Gallium–Indium co-substituted (YAG:Yb,Tm) samples were measured under 980 nm excitation. The effects of different In3+concentration on the luminescence properties of Gallium–Indium co-substituted (YAG:Yb,Tm) were also investigated. The fluorescence-lifetime investigation shows that the substitution of Ga3+ and In3+ has a significant influence on energy transfer between Yb3+ and Tm3+ in the YAG samples.

Luminescence of CNT coated LaPO4:Tm phosphors and their field emission lamp application

When the phosphor LaPO4:Tm was coated with carbon nanotubes (CNTs), carbon atoms were diffused into the phosphor lattice. Binding energy of La 3d and C 1s were not shifted by CNT coating, while that of O 1s was lowered slightly as a result of the formation of CO and CO bonds on the phosphor surface. CNT coating increased the atomic concentrations of O and C by 27.4% and 9%, respectively. Photoluminescence intensity decreased significantly, by 52%, when CNT concentration of 1.5wt% was coated. This is attributed to covering the phosphor with black CNTs/carbons and the formation of CO and CO bonds on the phosphor surface. Conversely, cathodoluminescence (CL) intensity was improved by a factor of 3.86 when 1.25wt% of CNTs was coated, attributing to improved conductivity, reduced charging, and increased CL excitation probability of the phosphor. The influence of CNT coating on the luminescence of LaPO4:Tm was compared with that of LaPO4:Eu phosphor. Blue CL was observed from LaPO4:Tm, it is potential for field emission lamp application.

Luminescence enhancement and potential application of sky-blue sulfide phosphor doped with promoter

The luminescence of the ZnS:Tm phosphor was enhanced by the addition of a KCl promoter, and a white phosphor was prepared for potential white-light applications. It was found that a high synthesis temperature and high TmF3 concentration promoted the substitution of Tm3+ ions for Zn2+ ions. KCl doping facilitated the growth of the hexagonal phase and decreased the phase transformation temperature of ZnS. In addition, the luminescence center concentration, excitation energy absorption, effective energy transfer, charge balance, and luminescence intensity of the phosphor were improved by the addition of the KCl promoter. The emission pattern and peaks of the ZnS:Tm,KCl phosphor were similar to those of the ZnS:Tm phosphor, indicating that the ligand field variation of Tm3+ caused by KCl doping was small. When the sky-blue ZnS:Tm,KCl phosphor was blended with a yellow ZnS:Mn,KCl phosphor in 1:1 weight ratio, white-light emission was observed under excitation from a 6-W ultraviolet lamp (1,350 μW/cm2, λ = 254 nm). The Commission Internationale de l’Eclairage coordinates were (0.36, 0.35), and the luminance intensity was 28.1 cd/m2.

A new photostimulated strontium-aluminate-based blue-green phosphor

We have proposed, experimentally demonstrated, and implemented a technique for producing a new photostimulated blue-green phosphor with increased photostimulated luminescence intensity via additional doping of the Sr4Al14O25:Eu,Tm phosphor with La3+. The photostimulated phosphor (FV-490M) has been commercialized and is used most widely in security and authentication applications, both as an individual phosphor and in combination with the photostimulated red phosphor SrS:Eu,Sm. When IR-stimulated, the combination phosphor exhibits a dynamic visual kinetic effect.

Preparation of CaF2:U phosphor by solid-state metathesis reaction

CaF2:RE phosphors have received attention of several research workers. CaF2:Sm2+ is well known as a solid-state laser material. CaF2:Dy and CaF2:Tm phosphors are used as phosphors for dosimetry of ionizing radiations through thermoluminescence. A new route to preparation of CaF2 by solid-state metathesis is reported. The method is very fast and CaF2 could be prepared in 10 min. Intense emission attributable to uranate group was observed in synthesized uranium-doped samples.

Synthesis, structure and photoluminescence properties of europium-, terbium-, and thulium-doped Ca3Bi(PO4)3 phosphors

A series of Eu(3+), Tb(3+), Tm(3+) singly and triply doped Ca3Bi(PO4)3 (CBP) phosphors were synthesized by solid-state reaction. Their structure and photoluminescence (PL) properties were first investigated in detail. Rietveld refinement analysis confirmed that the CBP has a cubic unit cell. Its space group was determined to be I4[combining macron]3d with cell parameters a = b = c = 9.941 Å and Z = 4. In addition, the Ca3Bi(PO4)3 shows both cation disorder and oxygen sublattice disorder. For the CBP:Eu(3+) phosphor, the charge transfer bands in the PLE spectra were different at 293 K and 4.3 K, and a model was presented to give a possible explanation for this phenomenon. CBP:Eu(3+) shows intense red emission due to (5)D0-(7)F2 transition and its integral emission intensity and quantum efficiency are higher than the commercial Y2O3:Eu(3+) phosphor under irradiation of 397 nm, indicating that the CBP:Eu(3+) phosphor might have potential application in the NUV range for solid-state lighting. The CBP:Tb(3+) and CBP:Tm(3+) phosphors show intense green and blue emission due to (5)D4-(7)F2 transition of the Tb(3+) ions and the (1)D2-(3)F4 transition of the Tm(3+) ions, respectively. The energy transfer from the Tb(3+) to Eu(3+) ions was also validated by the spectra and decay curves of the Tb(3+) ions. Tunable emission colors were obtained by triply doping Eu(3+), Tb(3+) and Tm(3+) activators in a single host and adjusting their relative ratio.

Hydrothermal Derived LaOF:Ln3+ (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) Nanocrystals with Multicolor-Tunable Emission Properties

A series of LaOF:Ln(3+) (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) nanocrystals with good dispersion have been successfully prepared by the hydrothermal method followed a heat-treatment process. Under ultraviolet radiation and low-voltage electron beam excitation, the LaOF:Ln(3+) nanocrystals show the characteristic f-f emissions of Ln(3+) (Ln = Eu, Tb, Sm, Dy, Tm, or Ho) and give red, blue-green, orange, yellow, blue, and green emission, respectively. Moreover, there exists simultaneous luminescence of Tb(3+), Eu(3+), Sm(3+), Dy(3+), Tm(3+), or Ho(3+) individually when codoping them in the single-phase LaOF host (for example, LaOF:Tb(3+), Eu(3+)/Sm(3+); LaOF:Tm(3+), Dy(3+)/Ho(3+); LaOF:Tm(3+), Ho(3+), Eu(3+) systems), which is beneficial to tune the emission colors. Under low-voltage electron beam excitation, a variety of colors can be efficiently adjusted by varying the doping ions and the doping concentration, making these materials have potential applications in field-emission display devices. More importantly, the energy transfer from Tm(3+) to Ho(3+) in the LaOF:Tm(3+), Ho(3+) samples under UV excitation was first investigated and has been demonstrated to be a resonant type via a quadrupole-quadrupole mechanism. The critical distance (R(Tm-Ho)) is calculated to be 28.4 Å. In addition, the LaOF:Tb(3+) and LaOF:Tm(3+) phosphors exhibit green and blue luminescence with better chromaticity coordinates, color purity, and higher intensity compared with the commercial green phosphor ZnO:Zn and blue phosphor Y(2)SiO(5):Ce(3+) to some extent under low-voltage electron beam excitation.

Determination of thermoluminescence kinetic parameters of thulium doped lithium calcium borate

For the first time kinetic parameters of thulium doped Lithium calcium borate (LCB) Thermoluminescence (TL) material are reported here. Irradiated LCB:Tm 3+ powder has revealed two intense TL glow peaks one at 510 (peak 1) and the other at 660 K (peak 2). Activation energy ( E ), frequency factor ( s ) and order of kinetics ( b ) of these peaks were determined by various heating rate (VHR), initial rise (IR), and peak shape (PS) methods. The trap depth and frequency factor determined for peaks 1 and 2 of LCB:Tm phosphor using VHR and IR methods are in good agreement. The average activation energy of peaks 1 and 2 obtained by these methods is 1.62 and 1.91 eV respectively. The frequency factors of peaks 1 and 2 are in the range of 10 13–16 and 10 12–14 sec −1 respectively. The E and s values estimated using the glow peak shape dependent parameters are relatively less compared to the values obtained from other methods. The large difference in these values is due to the complex nature of the glow curves. The order of the kinetics process for complex glow curve peaks could not be assigned on the basis of shape parameters alone but T m response on absorbed dose is to be considered for final confirmation. Glow peaks 1 and 2 of LCB:Tm 3+ obey first and general order kinetics respectively. ► Trap depth and frequency factor are determined for the peaks at 510 and 660 K of LCB:Tm. ► Parameters obtained by various heating rate and initial rise methods are in good agreement. ► Trap depth of peak 1 and peak 2 is 1.61 eV and 1.91 eV respectively. ► T m response to absorbed dose is used to distinguish a first order or non-first order kinetics.

Photoluminescence and structural properties of Ca 3Y(VO 4) 3:RE 3+ (=Sm 3+, Ho 3+ and Tm 3+) powder phosphors for tri-colors

An effort has been made in this paper to investigate a newly developed optical material, namely calcium yttrium vanadate Ca 3Y(VO 4) 3 (CYV) phosphor, in three different combinations such as CYV:Sm, CYV:Ho and CYV:Tm in order to identify red, green and blue (tri)colors, respectively. These rare-earth (RE) doped vanadate based phosphors were prepared by the co-precipitation method. The emission spectrum of CYV:Sm has shown an intense reddish orange emission transition 4G 5/2– 6H 7/2 at 602 nm with λ ex =305 nm, a green emission transition 5S 2– 5I 8 at 545 nm with λ ex =305 nm for CYV:Ho phosphor, and for CYV:Tm phosphor, an intense blue emission transition 1G 4– 3H 6 at 476 nm with λ ex =305 nm has been observed. Emission performances of these phosphors have been explained in terms of energy level diagrams. Besides the measurement of the photoluminescence (PL) of these phosphors, their nature and structural details have also been investigated from X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) studies.