Transitions Of Dy3 Research Articles

Structural, morphological and photoluminescence studies of Ca7Mg2P6O24:RE3+(RE3+= Tb3+, Dy3+) nanophosphor for solid state illumination

The Ca7Mg2P6O24:RE3+ (RE3+= Tb3+, Dy3+) nanophosphor material was synthesized by traditional wet chemical method. The XRD are used to determine phase and crystallinity of the synthesized sample; further FTIR, SEM, TEM, and PL properties were studied. The XRD pattern of prepared sample match well with standard JCPDS card no 00–020–0348, and it exhibits the rhombohedral structure along with space group R3c (161). The phosphate (PO4)3-group absorption band was observed at 990–1100 cm-1 in FTIR. Surface morphology (TEM analysis) reveals particle sizes in the range of 55–110 nm. The luminescence emission spectra of Ca7Mg2P6O24 phosphor activated by Tb3+ were studied at three different excitations: 352 nm, 370 nm, and 379 nm. The spectra show two emission peaks at 470 nm (blue) and 545 nm (green). These are due to the 5D4 → 7F6 and 5D4 → 7F5 transitions of Tb3+ ions. The highest intensity peak is located at 545 nm. The Ca7Mg2P6O24:Tb3+ phosphor's CIE chromaticity coordinates are (0.040, 0.316) at 491 nm and (0.265, 0.724) at 543 nm. These are in the blue and green areas on the edges of the CIE diagram, respectively. The photoluminescence emission spectra of Dy3+-doped Ca7Mg2P6O24 phosphor show two significant emission peaks located at 482 nm and 574 nm. These are caused by the 4F9/2 → 5H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, which produce blue and yellow light, respectively, with an excitation wavelength of 350 nm. The sharp peak position at 482 nm produces the strongest emission. The effect of concentration quenching in between the Dy3+-Dy3+ions and Tb3+-Tb3+ ions is due to dipole-dipole interaction. The CIE color coordinate is found to be (0.082, 0.156) at 482 nm and (0.471, 0.527) at 574 nm which lies in blue and yellow border of CIE diagram. The lifespan of Tb3+, Dy3+activated Ca7Mg2P6O24 nanophosphor of highest concentration is found to be 1.917 ms and 0.9985 ms respectively. On investigation, the synthesized Tb3+, Dy3+activated Ca7Mg2P6O24 nanophosphor can be potential for solid lightning devices & other display application.

α-Sr2SiO4:Ce3+, Dy3+, Na+ phosphors with abnormal thermal quenching properties for solid-state lighting applications

There is urgent need of thermally stable phosphors for fabricating high-performance white light emitting diodes (LEDs). In this paper, Sr2SiO4:0.02Ce3+,xDy3+, (0.02+x)Na+ phosphors were successfully synthesized by the solid-state reaction method and their luminescence properties were studied. Phase analysis shows that single-phasic α-Sr2SiO4 was prepared when x was greater than 0.006, while a mixed phase of α-Sr2SiO4 and β-Sr2SiO4 were obtained in the samples with x of 0.006 or less. When excited at 344 nm, there is a major emission band at 380–500 nm corresponding to the 5d-4f transition of Ce3+, and other emission peaks with a dominated one at 575 nm corresponding to the 4F9/2-6H13/2 transition of Dy3+. The as-developed Sr2SiO4:Ce3+,Dy3+,Na+ phosphors exhibit excellent thermal stability. To be specific, the intensity retention rate of 425 and 572 nm at 300 °C is as high as 103.6 % and 89.2 %, respectively. Furthermore, near-ultraviolet (nUV) chip-pumped white LED prototypes were assembled using the co-activated phosphor and commercial green and red phosphors, which demonstrate its great potential in high-power white LEDs for solid-state lighting applications.

White emitting Sr3Ga2Ge4O14: Dy3+ phosphors with high purity and good thermal stability

A series of white emitting phosphors Sr3Ga2Ge4O14: xDy3+ (x = 1, 3, 5, 7, 9 and 11 %) were synthesized by a high-temperature solid-phase method. All samples exhibit two emission peaks at 478 nm and 571 nm, corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+ ions, respectively. The optimal doping concentration of Sr3Ga2Ge4O14: xDy3+ phosphors was determined as 7 % mol, and the concentration quenching mechanism is confirmed as a dipole–dipole interaction. Finally, the temperature dependent luminescence spectra indicate that the synthesized Sr3Ga2Ge4O14: 7 % Dy3+ phosphors had good thermal stability.

Yellowish light emitting Dy3+ doped single phase – BaNb2O6 phosphors for solid state lighting applications

BaNb2O6:Dy3+ phosphors that emit cool light has been synthesized via traditional solid-state reaction technique. Developed samples show orthorhombic structure with space group C2221 according to X-Ray Diffraction (XRD) and Rietveld structural refinement. Observations made using a scanning electron microscope (SEM) show densely packed particles with irregular shapes in the micrometre range. Optical bandgap was also determined using Diffuse Reflectance Spectroscopy (DRS). When excited at 389 nm, the as-prepared phosphors show blue (481 nm) and yellow (577 nm) emissions, which correspond to the 4F9/2 → 6HJ (J = 15/2, 13/2) transitions of Dy3+ ions. A thorough investigation has been done on the energy transfer process between Dy3+ ions. The optimized phosphor's computed chromaticity coordinates for the Commission Internationale de L'Eclairage (CIE) are x = 0.392 and y = 0.414. The values of CIE chromaticity coordinates and correlated colour temperature (CCT) of 3995 K endorse near cool light emission from the phosphor. Thermal stability and temperature dependent photoluminescence spectroscopy were studied for optimized phosphor which revealed that the phosphor can be a potential material for lighting applications at higher temperature. The study also reveals that BaNb2O6:Dy3+ phosphor could be a promising candidate for near ultra-violet (NUV) excited, yellowish LED applications.

Dy3+ doped KCa(PO3)3 phosphor for white light generation: structural and luminescent studies

Using the traditional solid-state reaction approach, Dy3+ ions doped KCa(PO3)3 phosphors have been synthesized to investigate their luminescent properties to produce high-quality white light for solid-state lighting applications, particularly in white LEDs. x-ray diffraction (XRD) patterns were used to examine the structure and phase of the phosphors. Using scanning electron microscopy (SEM), the morphology of the as-synthesized phosphor has been investigated. Fourier transform infrared spectroscopy (FT-IR) has been used to investigate several vibrational bands seen in the phosphor. Using diffuse reflectance spectra (DRS), the as-synthesized phosphors’ optical band gap values have been estimated. When Dy3+ ions are excited at 350 nm, the photoluminescence (PL) spectra characteristics observed for the activated KCa(PO3)3 phosphor show strong white area emission due to both 575 nm, which is related to the 4F9/2 → 6H13/2 and 482 nm that is ascribed to 4F9/2 → 6H15/2 transition of Dy3+ ions. Additionally, the concentration quenching of Dy3+ ions doped at 4 mol% is seen in the PL spectra. Based on the observed PL spectra, the computed CIE chromaticity coordinates for the optimised KCa(PO3)3 phosphors are located in the deep white area. The lifespan of the as-titled phosphors decreases as the amount of Dy3+ ions increases in the host lattice. Additionally, the PL decay profiles shows a dual exponential behaviour when excited at 350 nm, with an emission wavelength at 575 nm. The lifetime values were used to calculate the quantum efficiency of the as prepared phosphors. On the basis of the results of the aforementioned studies, we wish to project Dy3+ ion doped KCa(PO3)3 phosphors as white light generating materials in w-LEDs and for other photonic applications.

Direct mechanochemical synthesis of CaMoO4 and Dy3+ doped CaMoO4 nanoparticles and their photoluminescent properties

Calcium molybdate (CaMoO4) and Dy3+ doped CaMoO4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO4 and Dy3+ doped CaMoO4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO4 samples contain absorption peaks corresponding to the MoO4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO4 and Dy3+ doped CaMoO4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F9/2 → 6H11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO4 nanoparticles can find application in different optical instruments.

Growth, spectroscopy and Dy3+→Tb3+ energy transfer of TbAl3(BO3)4 and Dy3+:TbAl3(BO3)4 crystals

TbAl3(BO3)4 and Dy3+:TbAl3(BO3)4 crystals were grown by the top-seeded solution method and the polarized optical spectra of the crystals were investigated at room temperature. Peak absorption cross-sections for the 6H15/2 → 4I15/2 transition of Dy3+ in the Dy3+:TbAl3(BO3)4 crystal are 1.2 × 10−21 cm2 at 453 nm and 0.6 × 10−21 cm2 at 452.4 nm for σ and π polarizations, respectively. Under excitation at 453 nm, a strong green fluorescence of Tb3+ around 541 nm was observed in the Dy3+:TbAl3(BO3)4 crystal due to the efficient energy transfer from Dy3+ to Tb3+ ions. Peak emission cross-sections for the 5D4→7F5 transition of Tb3+ in the Dy3+:TbAl3(BO3)4 crystal are 2.8 × 10−21 and 1.5 × 10−21 cm2 at 541 nm for σ and π polarizations, respectively. Fluorescence lifetime of the 5D4 level of Tb3+ is 1.4 ms and the efficiency of energy transfer from Dy3+ to Tb3+ ions is about 92% in the Dy3+:TbAl3(BO3)4 crystal. The results show that a commercial high-power 450 nm diode laser may be used as the pumping source for Dy3+/Tb3+ co-doped crystal to realize Tb3+ visible laser.

Structural and spectroscopic correlation in barium-boro-tellurite glass hosts: effects of Dy2O3 doping

In this study, a series of barium-boro-tellurite glass hosts with varying concentration of Dy2O3 doping (0 to 1.25 mol%) were made by melt-quenching method. A study was conducted to investigate how Dy2O3 dopants affect the physical and spectroscopic traits of glasses. Raw materials including barium oxide (BaO), tellurium dioxide (TeO2), boron oxide (B2O3), and dysprosium oxide (Dy2O3) were used to produce these glasses. XRD patterns of the samples showed a broad hump and absence of long-range periodic lattice arrangements, indicating their amorphous nature. The Raman spectral analyses displayed the various vibration modes where the most intense band caused by BaO vibrations at 300 cm-1 and 450 cm-1 corresponding to the symmetric stretching vibration mode of Te–O–Te intra-chain bridges. The peak at 750 cm-1 was due to TeO4 and Te-O-Te vibration modes. The value of optical band gap energy was decreased from 3.155 to 2.1894 eV and then increase at higher Dy2O3 level (0.75 to 1.25 mol%). At Dy3+ contents between 0.25 to 1.25 mol% seven absorption bands were observed at 390, 424, 452, 750, 797, 895 and 1092 nm due to the electronic transitions in Dy3+. The glass refractive indices were raised from 2.3563 to 2.6584 and then decreased at higher Dy2O3 contents which was mainly because of the generation of more bridging oxygen (BO) in the glass matrix. The value of glass electronic polarizability and oxide ions polarizability calculated using LorentzLorenz equation showed a decrease with the rise of Dy2O3 contents, which was ascribed to the presence of fewer non-bridging oxygen (NBO). The optical basicity of the proposed glass hosts was calculated using Duffy and Ingram equation which was decreased with the increase of doping contents. In addition, the optical transmission was increased and reflection loss was reduced with increasing Dy+3 levels. The value of metallization parameter below 1 proved the true amorphous nature of the prepared samples. All the glasses revealed blue and yellow photoluminescence emission peaks due to 4F9/2→ 6H15/2, and 4F9/2 →6H13/2 transitions in Dy3+, respectively. The proposed glass compositions may be beneficial for the advancement of solid-state lasers.

Synthesis, crystal structure and luminescent properties of a quinary borate-phosphate compound CsNa2Dy2(BO3)(PO4)2

Abstract Borate-phosphates exhibit a wide range of compositional and structural diversity, making them ideal hosts for luminescent materials. In this work, a new borate-phosphate compound CsNa2Dy2(BO3)(PO4)2 has been prepared under high temperature solution growth method. It crystallizes in an orthorhombic space group Cmcm with the following lattice parameters determined by single-crystal X-ray diffraction: a = 6.9709(5), b = 14.9699(11), c = 10.6480(8) Å, z = 4. Its structure contains isolated BO3 planar triangles and PO4 tetrahedra, which are interconnected by Cs+, Na+ and Dy3+ ions. Solid solutions of CsNa2Y2(1−x)Dy2x (BO3)(PO4)2 (x = 0 − 0.08) are prepared and exhibit a yellow emissive luminescence by near-UV excitation due to the 4F9/2 → 6H(13/2, 15/2) transitions of Dy3+. The optimized concentration of Dy3+ is x = 0.01, and if over this critical value, the luminescent intensity will decrease due to concentration quenching. The Commission International de L’Eclairage (CIE) coordinates for CsNa2Y1.98Dy0.02(BO3)(PO4)2 are (x = 0.377, y = 0.404), corresponding to yellow color. The prepared phosphor may serve as a yellow phosphor for NUV-excited LEDs.

Deconstructing excitation transitions in Dy3+-doped CaWO4 to develop a new ratiometric luminescent thermometry for achieving ultra-high sensing sensitivity

In this paper, we propose a new ratiometric thermometric strategy with high sensitivity enabled by deconstructing the CTB and Dy3+ excitation transitions in CaWO4:Dy phosphors.

White light-emitting ZnO:Dy3+ nanophosphors: delving into the spectroscopic parameters via Judd-Ofelt analysis.

Developing a single-phase white emitting nanophosphor with high quantum efficiency has become a hotspot for scientific world. Herein, single-phase white-light emitting Zn1-xO:xDy3+ nanophosphors have been synthesized via a sonochemical method. X-ray diffraction analysis and Raman spectroscopy-based investigations confirmed the hexagonal wurtzite phase for Zn1-xO:xDy3+ nanophosphors with preferential growth along the (101) plane. Scanning electron microscopy images showed the formation of a ribbon-shaped morphology with a diameter of ∼25 nm. The emission spectra of the Dy3+-activated ZnO nanophosphors exhibited three distinct peaks, namely blue (480 nm), yellow (572 nm), and red (635 nm) emissions, under near-UV excitations related to the 4F9/2 → 6HJ (J = 15/2, 13/2, and 11/2) transitions of Dy3+ ions. The values of CIE chromaticity coordinates for the optimized phosphor (x = 0.329, y = 0.334) with correlated color temperature (CCT) of 5657 K indicated cool white-light emission from the phosphor. The thermal stability of ZnO:Dy3+ nanophosphors was probed by temperature-dependent luminescence. Quantitative evaluation of Judd-Ofelt intensity parameters, radiative parameters, luminescence decay, and quantum efficiency of Zn1-xO:xDy3+ using the J-O theory suggests that these nanophosphors are promising luminescent media for commercial white LEDs and other display devices.

Structural, photoluminescence and energy transfer investigations of novel Dy3+ → Sm3+ co-doped NaCaPO4 phosphors for white-light-emitting diode applications.

In this study, Dy3+-doped and Dy3+/Sm3+ co-doped NaCaPO4 white-emitting polycrystalline phosphor samples were synthesized using a solid-state reaction method. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), and Photoluminescence (PL) analysis. The phase purity characterization and crystal structural analysis were done using the Rietveld refinement-based FullProf Suite software. The Rietveld refinement result confirms single-phase formation for both Sm3+ and Dy3+/Sm3+ co-doped NaCaPO4 samples with an orthorhombic structure and with a monotonic change in lattice parameters with doping. The PL studies of the Dy3+-doped samples revealed two emission bands. However, at 352 nm, the Dy3+/Sm3+-co-doped samples revealed distinctive emission bands for both ions. The emission peaks at 480 nm (blue) and 573 nm (yellow) are related to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions; however, the emission peaks at 600 nm and 647 nm are attributed to the 4G5/2 → 6H7/2 and 4G5/2 → 6H7/2 transitions of Sm3+ ions. The intensity of the Dy3+ emissions decreased as the Sm3+ levels increased but the emission intensity of the Sm3+ ions increased. The co-doping of Sm3+ ions in Dy3+-doped phosphors results in unique characteristics due to the energy transfer (ET) from Dy3+ → Sm3+ ions. The effectiveness of this ET from Dy3+ → Sm3+ ions is positively correlated with the dopant amounts of the Sm3+ ions. The interaction mechanisms have been identified as dipole-dipole based on Dexter's energy transfer and Readfield's approaches. All decay curves can be adequately fitted via bi-exponential functions, suggesting the movement of energy between Dy3+ → Sm3+ ions. Temperature-dependent PL measurements and CIE color coordinate analysis reveal excellent luminescent properties, making these Dy3+/Sm3+ co-doped phosphors advantageous for white light-emitting diode (WLED) technologies.

Spectral tunability of K2Lu(WO4)(PO4): Dy3+, Eu3+ phosphors and remote luminescent layers for high-quality white light

Dy3+ and Eu3+ co-doped phosphors have been emerged as potential candidate to generate high-quality white light under the ultraviolet (UV) or near ultraviolet (NUV) excitation for health and comfort lighting. Herein, K2Lu(WO4)(PO4) crystal has been newly developed to accommodate rare earth ions, such as Dy3+ and Eu3+ ions, to achieve spectral tunability of high-quality white light. Under NUV excitation, Dy3+ singly-doped K2Lu(WO4)(PO4) phosphors exhibit the desired blue emission at 486 nm and yellow emission at 575 nm, attributed to the electric dipole transition 4F9/2 → 6H15/2 and the magnetic dipole transition 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. Interestingly, the emission color can be facilely adjusted from cold white light to pink light under 365 nm NUV excitation due to the co-doping of Eu3+ ions in K2Lu(WO4)(PO4): 0.05Dy3+ sample. Further, the remote luminescent layers containing K2Lu(WO4)(PO4): 0.05Dy3+, 0.20Eu3+ phosphor can be printed on glass substrate by screen printing technique to generate high-quality white light with the correlated color temperature (CCT) of 5433 K and color rendering index (CRI) of 87. Moreover, the remote luminescent layers exhibit better heat dissipation performance compared to conventional encapsulated LEDs and can be used as a multicolor emitting candidate for high-power white LEDs.

Synthesis and Characterization of White Light Emission of Dy3+ Doped Gd2O3 Phosphors

Dy3+ ion doped Gd2O3 phosphors with varying concentrations were synthesized successfully by hydrothermal process. The XRD patterns and TEM images of prepared samples were well-studied. Upon the emission at λem = 573 nm, the excitation spectra consist of several peaks which denote the characteristic lines of the 4f-4f or 4f-5d intra-configurational transition of Gd3+ and Dy3+ ions. In the emission spectrum obtained by excitations at 234 nm and 273 nm, consist of two characteristic band obtained at 485 and 573 nm, which are attributed to 4F9/2→6H15/2 (blue) and 4F9/2→6H13/2 (yellow) transitions of Dy3+ ion, repectively. The photoluminescence lifetime are found to be at around 0.599-1.200 ms. The CIE Chromaticity coordinates showed the prepared samples could be used as a white light emitting phosphor applied in near UV region.

Photoluminescence and thermoluminescence properties of pure and rare-earth-doped ZrO2 prepared by Pechini-type sol-gel.

In this article, photoluminescence (PL) and thermoluminescence (TL) properties of ZrO2 , ZrO2 :Dy3+ , ZrO2 :Dy3+ -Gd3+ , ZrO2 :Dy3+ -Yb3+ , ZrO2 :Dy3+ -Er3+ , and ZrO2 :Dy3+ -Sm3+ phosphors synthesized by the Pechini method were investigated. The crystal structure, thermal properties, morphology, PL and TL properties were investigated using X-ray powder diffraction (XRD), differential thermal analysis/thermogravimetric analysis (DTA/TGA), scanning electron microscopy (SEM), PL and TL, respectively. The room temperature emission bands corresponding to 4 F9/2 →6 HJ (J= 9/2, 11/2, 13/2 and 15/2) transitions of Dy3+ ions were measured. The phosphors were analysed using Tm -TSTOP , variable dose, and computerized glow curve fitting methods. Reusability, dose-response, and fading characteristics were investigated. The phosphors have a natural TL emission that vanished by heating treatment. Moreover, new peaks with similar properties to the natural emissions were observed after high-dose irradiation and long-term fading experiments. The glow curves of the phosphors have 13 individual peaks and many low- and high-temperature satellite peaks. The origin of the peaks is ZrO2 host material and doping with rare-earth ions (Gd3+ , Dy3+ , Yb3+ , Er3+ and Sm3+ ) does not lead to a new glow peak. The dopants cause drastic changes in individual peak intensities of ZrO2 .The initial fading rates of all the phosphors are relatively fast, but they slow down as time goes on.

Synthesis, spectral characteristics and energy transfer of SrLa2Al2O7:Mn4+, Dy3+

Researchers usually co-dope other ions in Mn4+ doped phosphors to improve and regulate their luminescence properties for the improvement of their practicality. Here, we synthesize SrLa2Al2O7:R (RDy3+, Mn4+, and Dy3+/Mn4+) samples by solid-state method in air. The crystal structure and phase purity are confirmed by XRD patterns of samples. We investigate the morphology, luminescence properties, optimal doping concentration of Dy3+ and Mn4+ ions, lifetimes as well as the energy transfer from Dy3+ to Mn4+ ions. We observe yellow emission of SrLa2Al2O7:Dy3+ under excitation 355 nm in the region from 450 nm to 650 nm with chromaticity coordinates (0.4684, 0.5035) due to the 4F9/2 → 6H15/2 and 6H13/2 transitions of Dy3+ ion. SrLa2Al2O7:Mn4+ under excitation 355 nm emits far-red light in the region from 650 nm to 810 nm with chromaticity coordinates (0.7141, 0.2858) due to the transition 2Eg → 4A2g of Mn4+ ion. SrLa2Al2O7:4mol%Dy3+, 0.5mol%Mn4+ under excitation 355 nm contains the emission of both Dy3+ and Mn4+, and shows red emission with chromaticity coordinates (0.5899, 0.4055). The energy transfer process from Dy3+ to Mn4+ ions in SrLa2Al2O7:Dy3+, Mn4+ is verified by the spectral characteristics. The luminous mechanisms of samples are analyzed by energy level diagrams of Dy3+ and Mn4+ ions.

A novel thermally-stable single-phase phosphor Ca2InTaO6:Dy3+ for NUV-excited white LEDs

The work focuses on the utilization of the conventional solid-state sintering procedure to synthesize white phosphors Ca2InTaO6:xDy3+ (0.02 ≤ x ≤ 0.12). Utilizing X-ray diffraction, the phase structure of samples was examined, and the crystal structure was refined using the Rietveld method. A scanning electron microscope was used to analyze the microstructure of sample. First-principles calculations confirm that the indirect bandgap of Ca2InTaO6 is 3.786 eV. The luminous properties and energy transfer mechanism of Ca2InTaO6:xDy3+ were studied using photoluminescence spectroscopy. The 4F9/2 → 6H13/2 transition of Dy3+ ions is responsible for the greatest emission peak, which was measured at 575 nm. According to research, the lifespan falls as the concentration of Dy3+ doping amount rises because of frequent interaction and energy transfer between Dy3+ ions. The correlated color temperature of the W-LEDs packaged with Ca2InTaO6:0.08Dy3+ is 4677 K and CIE 1931 chromaticity coordinates are (0.3578, 0.3831). Meantime, the phosphor also shows outstanding temperature stability property, which maintains 83.8% of its initial emission intensity at 450 K (activation energy of 0.1467 eV). The W-LEDs retain their performance for 100 min when powered at 3.4 V voltage and 600 mA current, demonstrating the packed W-LEDs' sustained operation at high temperatures.

White-light emitting BaAl2O4/CaAl4O7:x% Dy3+ (0 ≤ x ≤ 3) mixed phase nanophosphors synthesized using citrate sol-gel method

Novel mixed phase BaAl2O4/CaAl4O7 (BC) and BC: x% Dy3+ (0 ≤ x ≤ 3) nanophosphors were synthesized by the citrate sol-gel method. The morphology changed as x%Dy3+ varied. The patterns showed that the BC nanophosphors matched well with the monoclinic CaAl4O7 and hexagonal BaAl2O4 structures. Moreover, the structure of BC was not influence by the dopant. The dopant is mainly located in the BaAl2O4 phase. The crystallite sizes were estimated to be in the nanoscale order. The photoluminescence (PL) results showed that the emission was quenched for BC: x% Dy3+ (x > 2.4) be due to the quadrupole-quadrupole interaction. The emission peaks at 325, 482 and (563 and 576) nm were assigned to the bandgap defects of BC, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The International commission on illumination (CIE) showed the dopant (Dy3+) had changed the emission color from blue to white. This showed that the BC: x% Dy3+ (1.2 ≤ x ≤ 3) nanophosphors were potential candidates for white-light LEDs.

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 4 F9/2 → 6 H15/2 and 4 F9/2 → 6 H13/2 transition of Dy3+ respectively. The PL emission spectra of CaAlBO4 :Eu3+ phosphor shows characteristics bands observed around 591 and 613 nm, which corresponds to 5 D0 → 7 F1 and 5 D0 → 7 F2 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 4 G5/2 → 6 H7/2 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.

Optical properties and tunable luminescence of Ce3+/Dy3+ doped lithium borate glasses for photonic applications

Optical absorption and photoluminescence properties of novel lithium borate glasses, (B2O3)-(MO)-(Li2O)–(Bi2O3) where M stands for Ca, Mg or Sr, doped with Dy and Ce ions have been investigated. The fundamental optical absorption edge of these materials is observed in the region of 315–390 nm, and depends on the nature of alkaline-earth metals used as network modifiers. The photoluminescence spectra of Dy-doped glasses reveal two intensive emission bands in the visible range, which correspond to 4F9/2→6H15/2 (486 nm) and 4F9/2→6H13/2 (580 nm) transitions of Dy3+ ions. Ce-doped glasses show one broad band in the visible range, which corresponds to the 2D →2F5/2 (340 nm) transition of Ce3+ ions. Three photoluminescence lines (980 nm, 1010 nm and 1150 nm) attributed to the Dy3+ ions electronic transitions are observed in the near-IR region of the spectrum for Dy-doped glasses, while only one at 1150 nm is observed for the Dy/Ce co-doped glasses. Peculiarities of excitation energy transfer between rare-earth activator ions are discussed. These glasses are shown to be a promising host matrix for rare-earth doping.