Doped Phosphors Research Articles

Effect of Zn2+, S2−, Mo4+ and V5+ single doped BiTa7O19:Er3+/Yb3+ on upconversion luminescence intensity under 980 nm laser excitation

On the basis of BiTa7O19 (BTO):0.1Er3+/0.4 Yb3+, Zn2+, S2−, Mo4+ and V5+ single doped upconversion phosphors (UCP) were successfully prepared by solid phase sintering. The lattice structure, particle size and diffuse reflectance spectra were measured by X-ray diffraction, scanning electron microscope and spectrophotometer. Upconversion luminescence (UCL) spectra of these UCP were investigated under 980 nm laser excitation with power density from 1.82 to 124.99 W/cm2. Zn2+ doped UCP can obtain the highest UCL intensity when excitation power density is less than 56.91 W/cm2, and Mo4+ doped UCP can obtain the highest UCL intensity when excitation power density is from 56.91 to 124.99 W/cm2. The UCL intensity of all samples increases first and then decreases with the increase of excitation power. By measuring UCL intensity changes with the excitation power of the UCP mixing with BN and UCP in vacuum and atmosphere, the experimental results show that the increase of temperature caused by laser excitation is the reason for the decrease of UCL intensity under high power excitation. Utilizing LIR technology, it is proven that at high power 90.95 W/cm2, Mo4+ and Zn2+ single doped can decrease and increase the UCP temperature under the same power density excitation compared with BTO:0.1Er3+/0.4 Yb3+, respectively. The maximum relative temperature sensitivity of all UCP is calculated in the range of 0.00767–0.00854 K−1 at 303 K. All experiments show that Zn2+ and Mo4+ single-doped UCP are suitable for temperature sensing and luminescence imaging under low and high-power excitation, respectively.

Photoluminescence and EPR spectroscopic studies on narrowband ultraviolet-B (NB-UVB) emitting trivalent gadolinium-doped CaAl4O7 material for phototherapy lamps

Using the sol-gel process, a series of Gd3+ doped CaAl4O7 samples were fabricated. Their crystal characteristics, surface morphologies, and spectral characteristics were analyzed using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. XRD analysis reveals that the prepared phosphor exhibits a single monoclinic phase, indicating a well-defined crystal lattice. Under the excitation wavelength of 272 nm, weak and strong emission peaks were identified at 307 nm and 314 nm, which correspond to 6P5/2 → 8S7/2 and 6P7/2 → 8S7/2 transitions, respectively. A strong electron paramagnetic resonance (EPR) signal of the CaAl4O7:Gd3+ phosphor was observed at geff ∼ 2.16 and 1.94 along with several weak EPR signals that were observed at geff ∼ 14.8, 9.7, 5.6, 4.8, 3.7, 3.16, 2.7 and 1.5. The intense narrowband at 314 nm in the ultraviolet-B region makes prepared phosphor a promising candidate for phototherapy lamp applications. This study presents a comprehensive investigation of the Gd3+ doped CaAl4O7 phosphor, addressing its structural, and luminescent properties, which contributes to a deeper understanding of this material for various technological applications.

Structural and luminescence performance of the Eu3+ doped alkaline combined metal oxide-based sodium phosphate phosphors; NaMPO4 (M = Mg, Ba, and Ca) for LED applications

The present research module is about the synthesis of Eu3+ ions-doped NaMPO4(M = Mg, Ba, and Ca) phosphate phosphors by the solution combustion synthesis method. The phase formation and chemical structures of alkaline combined metal oxide-based sodium phosphate phosphors are characterised by X-ray powder diffraction (XRD) and FT-IR measurements. Optimized crystal geometries were generated by employing VESTA software. The crystallite size was calculated from the full width at half maximum (FWHM) of the diffraction peak using the Scherrer formula. G-Fourier transformation software (G-FT) was adopted for generating electron density mapping of NaMgPO4 phosphors, 2D mapping, and 3D chicken plots showing crystal sites occupied by the compound’s constituent elements. The particle size distribution was confirmed by XRD diffraction, and SEM analysis found approximately 12 μm. UV–visible and photoluminescence spectroscopy uncover the optical traits of the prepared phosphor. Photo-emissions of Eu3+doped alkaline combined metal oxide-based sodium phosphate phosphors were monitored at possible excitation wavelengths. The orange-red peak observed at 592 nm and 598 nm occurs due to 5D0-7F1 electric dipole transitions. The peak observed at 618 nm corresponds to the forbidden f-f transitions 5D0-7F2. It is worth mentioning that absorption bands originating from the corresponding 5D0-7F2 transition widen the band region; hence, the stark effect becomes complicated. A low-intensity peak of 688 nm was observed in the NaCaPO4 phosphors, attributed to the 5D0-7F3 transition. Chromaticity coordinates and energy level transitions may determine the colour emission materials. The CIE coordinates of NaMPO4:Eu3+phosphors exhibit reddish emission and find application in light-emitting diodes (LEDs) and illuminating displays.

Luminescence Properties of Ce-Doped Di-Calcium Magnesium Disilicate Ca2MgSi2O7:4 mol%Ce

Dicalcium magnesium disilicate (Ca2MgSi2O7) doped with cerium rare earth ions has been examined for its optical and photonic characteristics and applicability for radiation dosimetry applications. Mono-calcium aluminate that has cerium added to it, has been shown to be an excellent dosimeter with a linear response up to roughly 4 kGy of radiation exposures. Maximum TL emission is achieved at 4 mol% cerium dopant concentration. The clearly visible two peaks that were detected at 381.13K and 566.87K can be used as a high-temperature dosimetry advance. In this study, we reported the preparation technique and luminescence properties such as TL, ML, and PL of Ce3+ doped dicalcium magnesium silicate phosphors. The phosphors were prepared by the solid-state reaction method. The TL glow curves were recorded for all different concentrations of Ce- doped phosphors.

Tb-doped MgAl2O4 phosphors: A study of structural and luminescence characteristics

In the MgO–Al2O3 system, magnesium aluminate spinel (MgAl2O4) is a technologically significant compound due to its unique properties, including a high melting point, low thermal conductivity, excellent thermal shock resistance, chemical inertness, and robust mechanical strength. This compound has diverse applications in refractory materials, catalyst supports, moisture sensors, nuclear techniques, insulating materials, and even military applications. While rare-earth elements are commonly used as dopants in luminescent materials, limited research exists on doping of Tb3+ ions in magnesium aluminate. This study investigates the luminescence properties of Tb3+ doped synthesis magnesium aluminate materials, shedding light on this underexplored area. The combustion method is employed for synthesis, known for producing nano-sized powders with exceptional luminescent properties. Additionally, this study explores Sm3+ ion doping in magnesium aluminate materials and their luminescence properties. Using the combustion synthesis method, structural attributes of Tb3+−doped MgAl2O4 nanophosphors are meticulously examined. Through X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses, coupled with excitation and emission spectra, a comprehensive investigation of the luminescent provide behavior at room temperature is provided. The XRD data reveal Tb3+ doped MgAl2O4 phosphors exhibit a single phase with face centred cubic structure belonging to the Fd3m‾ space group, consistent with the standard JCPDS files (No. 21–1152). Excitation and emission spectra offer valuable insights into the energy transitions within the Tb3+−doped MgAl2O4 phosphors. Furthermore, the study explores the effects of varying Tb3+ ion concentrations on the luminescent properties, revealing an optimal doping concentration of 5 wt% Tb for maximizing emission intensity. Concentration quenching, primarily attributed to dipole-dipole (d-q) interactions, is observed at higher Sm3+ concentrations. In conclusion, this research enhances our understanding of rare-earth ion doping in luminescent materials and highlights the potential applications of Tb3+−doped MgAl2O4 nanophosphors, which offer promise for various technological applications, including lighting and displays.

Mechanoluminescence and photoluminescence properties of Eu3+ -activated SrGa2 O4 phosphors.

Red-emitting Eu3+ activated SrGa2 O4 phosphors were synthesized using a conventional solid-state reaction method. The structural, optical, and luminescence properties were systematically investigated. The synthesized phosphors are single phase with a monoclinic structure. There are no significant changes in the phase and the crystal structure of the host matrix after incorporating Eu3+ ions. The undoped and Eu3+ doped SrGa2 O4 phosphors exhibited good mechanoluminescence (ML) emission without any irradiation with ultraviolet (UV) or gamma rays. Eu3+ -activated SrGa2 O4 phosphors have prominent red emission attributed to 5 D0 → 7 F2 forced electric dipole transition excited at 395 nm. The colour coordinates and purity of the SrGa2 O4 : 0.08 Eu3+ phosphor were calculated to be (0.6102, 0.3810) and 97.6%, respectively. The quantum efficiency is 12.68%, and was better than that of commercially available red phosphors. The ML and photoluminescence studies revealed that the synthesized phosphors can act as potential candidates for stress sensors, UV or near-UV light-emitting diodes (NUV LEDs) and components of phosphor-converted white light-emitting diode (pc-WLED) applications.

Eu3+ doped CaWO4 nanophosphor for high sensitivity optical thermometry

Eu3+ doped calcium tungstate phosphors were obtained by using sodium citrate as chelating agent in hydrothermal process. The structure and morphology of the samples were indicated by XRD and the FE-SEM. The samples prepared by us are scheelite structure. In addition, the particle size of sample decreases with sodium citrate dosage increasing, and finally reaches the nanoscale. The average particle size is 90 nm. The temperature measurement properties of phosphors were tested. It can be seen from test results that the thermal quenching behavior of Eu3+ and WO42- luminescence has obvious difference. Hence, the FIR of Eu3+ and WO42- can be used to express temperature. The maximum relative sensitivity increases with the decrease of particle size and the maximum is 4.3% K−1 (303 K, 90 nm). Moreover, the color of sample luminescence altered continuously from blue to pink-red as the temperature increased. The luminous color of the sample can be used to roughly estimate the temperature. Therefore, the CaWO4: Eu3+ nanophosphor are promising materials for optical thermometry.

Blue-yellow emitting Dy3+ doped K2Y2B2O7 novel phosphor for WLED application

Blue-yellow emitting Dy3+ doped K2Y2B2O7 novel phosphor for WLED application

UV and blue excited tunable emission of thermally stable Bi3+ sensitized Eu3+ doped calcium aluminozincate phosphor for photonic applications

Bi3+/Eu3+ co-driven calcium aluminozincate (CAZ) phosphor prepared by sol–gel route. Structural analysis was conducted based on X-ray diffractogram. Scanning Electron Microscope images were recorded using Carl Zeiss microscope. Luminescent traits of the said phosphors were identified using excitation and emission spectroscopy at room temperature and elevated temperature. The emission spectra recorded at room temperature under different excitations exhibit variation in spectral behavior. The Commision Internationale de-lElcairage coordinates shown in chromaticity diagram indicate the change in emission hue as pure blue, bluish red and finally pure red by varying the excitation wavelengths. The temperature dependent emission spectra show decrease in emission intensity with temperature and activation energy found to be 0.280 eV. The decay curves were also recorded to determine lifetime and study energy transfer between Bi3+ and Eu3+ ions. Auzel’s fit conducted based on the decay lifetimes helps in evaluating quantum efficiency theoretically. All these investigations authorize the potential of Bi3+/Eu3+ doped CAZ phosphors for their utilization as color-tunable phosphor in photonic applications.

Small Stokes shift and high thermostability in Ce3+ doped K2BaPO4F phosphors

Novel K2BaPO4F:Ce3+ phosphors with strong violet-emission and high thermostability were synthesized by a traditional high-temperature solid-state reaction method. The phase composition and crystal structure were investigated in detail by XRD refinement. DFT calculations based on refined crystal structure were performed. A bright emission in the range of 340–390 nm with a small Stokes shift has been observed when excited at about 323 nm in K2BaPO4F:Ce3+ phosphors. The temperature-dependent PL spectra from 80 to 500 K were investigated systematically. The best doping concentration of K2BaPO4F:xCe3+ phosphors was verified and the concentration quenching mechanism was also confirmed. When the temperature increased from 80 K to 500 K, the emission intensity still remains 53 %. The thermal quenching mechanism was explained using the crystal structure investigation and DFT calculation. The strong near-ultraviolet emission intensity and ultra-high thermal stability indicating that the prepared K2BaPO4F:Ce3+ phosphors have potential applications in anti-counterfeiting and solid-state lighting.

An insight into Judd-Ofelt analysis and non-contact optical thermometry of LiCa2Mg2V3O12: Dy3+ phosphors for multifunctional applications

A series of Dy3+ doped LiCa2Mg2V3O12 phosphors have been synthesized by solid state method. The phase composition of the phosphor has been analyzed by X-ray powder diffraction and confirms a cubic phase with Ia-3d space group. The scanning electron microscope images of LiCa2Mg2V3O12:xDy3+ phosphor reveals the surface morphology and is further investigated by its energy dispersive X-ray spectrum. The elemental mapping analysis displays the uniform composition of the elements present in the phosphor. The band gap energy of the phosphors has been determined from the diffuse reflectance spectra. The Judd-Ofelt intensity parameters are determined from the absorption spectra and follows the trend Ω2 > Ω6 > Ω4. The photoluminescence spectra of phosphors excited at 338 nm have intense emission at 494 and 576 nm corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transition and is ascribed to the magnetic and electric dipole allowed transition respectively. The radiative parameters for the optimum dopant concentration x = 0.08 has been calculated. Temperature dependent PL spectra of phosphor displays the diverse thermal response of VO43− group and Dy3+ ion and this can be utilized for the development of thermosensor based on fluorescence intensity ratio (FIR). The phosphor have maximum absloute and relative sensitivity values of 0.0063 K−1 and 0.41% K−1 in the temperature range of 80–400 K. The optical properties of the phosphor suggest that it find applications in the fields of solid-state lighting, temperature sensing, optoelectronic devices and W-LEDs.

Cathodoluminescence and Photoluminescence Studies of Undoped and Eu2+ Doped SrAl2O4 Phosphors Prepared by Combustion Method

Cathodoluminescence and Photoluminescence Studies of Undoped and Eu2+ Doped SrAl2O4 Phosphors Prepared by Combustion Method

Photoluminescence studies of Eu3+ doped bismuth silicate based phosphor for plant grow LEDs

Artificial red lights of good quality are essential for indoor plant growth as it has a wide spectrum effects on photosynthesis rate and photomorphogenic processes of organic plant growth cycle. In present work we report on Eu3+ doped Bi4Si3O12 (BSO) phosphor for spectroscopic implication in smart plant grow LEDs. Eu3+ activated series of Bi4Si3O12 phosphor have been prepared via traditional solid-state reaction method. Crystal structure and phase formation characterization is determined by using X-ray diffraction (XRD). Photoluminescence spectra of prepared phosphor shows broad excitation spectra ranging from 200 to 530 nm. The optimal Eu3+ doping concentration observed at 3 mol%. Emission spectra observed under the excitation of 270 nm shows broad emission band at 469 nm along with other characteristic peak at 500 nm-710 nm. Observed emission peaks at 622 nm, 656 nm and 702 nm were chosen opt for plant grow lights. The phytochrome PFR absorption spectra of plants matches well with the emission band of our Eu3+ doped BSO phosphor and can be considered as a viable choice for solid state lighting and plant grow light LEDs.

Nd3+ emission in the garnet structure of LiCa3ZnV3O12 phosphor

Nd3+ doped vanadate phosphors are well known, mainly for their suitability for solid-state laser applications. Garnet structures are also explored for such purposes. LiCa3ZnV3O12 is one of them. Luminescence in this host has not yet been investigated. The luminescence characteristics of LiCa3ZnV3O12:Nd3+ are reported here. Two types of emissions have been observed. The self-activated luminescence could be observed under UV excitation. The characteristic emission of Nd3+ is also observed. Apart from the f–f excitation, an efficient host sensitization of Nd3+ luminescence is observed. The LiCa3ZnV3O12:Nd3+ phosphor showed an intense Near Infrared emission at 1068 nm due to the transition of 4F3/2 → 4I9/2, for 350 nm excitation.

About the nature of luminescent bands in undoped and Eu2+ doped SrAl2O4 phosphors

In this paper we report the luminescence properties of nanosized undoped and Eu2+ (1%) doped SrAl2O4 phosphors. The samples were prepared by combustion method at 600 °C followed by annealing of the resultant combustion ash at 1000 °C in a reductive (Ar + H2) atmosphere. Photo luminescence (PL) and cathodoluminescence (CL) analyses were applied to characterize the phosphors. The qualitative energy level scheme of doped crystal SrAl2O4:Eu2+ and nature of defects in undoped phosphor is proposed and discussed. Within a simplified model of a single vibration and linear vibronic coupling the shape-function of the vibrationally assisted band (Pekarian) is analyzed with the emphasis on the vibrational structure. We propose an approximate approach to pass from the discrete Pekarian distribution to the structureless crystal field spectra taking into account phonon dispersion. This approach is expected to be useful for the description of the shape of the bands when the electronic levels are close to the conduction band of the host crystal.

An investigation about the ability to change color and the way energy is transferred of NaYMgWO6:RE3+ (RE3+ = Tm3+, Dy3+, Tm3+/Dy3+): A new type of single-phase white phosphor for WLEDs

Novel NaYMgWO6:Tm3+, Dy3+ phosphor is synthesized by solid-state reaction method in air. The phase structure was meticulously analyzed through XRD and Rietveld refinement techniques. Dy3+ doped NaYMgWO6 phosphors emitted yellowish-white light, which was observed. Surprisingly, the introduction of Tm3+ ions resulted in white-emitting, which was further studied with the aid of a spectrometer. By fixing the concentration of Tm3+ ions and subsequently adjusting the co-doping concentration of Dy3+ ions or altering the excitation wavelength, the CIE coordinates of NaYMgWO6:Dy3+, Tm3+ phosphors shifted from the blue-violet region to the yellowish-white region. In particular, when b = 0.2 mol, there was efficient energy transfer from Tm3+ to Dy3+, with an energy transfer efficiency of 95.1 %. The gradual decrease of the lifetime at 454 nm monitoring implies that there is indeed an energy transfer process from Tm3+ to Dy3+ and that the probability of energy transfer from Tm3+ to Dy3+ gradually increases with increasing Dy3+ concentration. These findings indicate that NaYMgWO6: aTm3+, bDy3+ phosphors offer a novel approach to researching single-phase white phosphors.

Photoluminescence study of Sr3Al32O51:Eu3+ phosphor for Solid state lighting applications

Sr3Al32O51:Eu3+ phosphor prepared successfully by simple combustion method. Prepared matrix synthesized for different percentage of composition for rare earth Eu3+ = (0.5, 1.0, 1.5, 2.0 and 2.5). Photoluminescence property was taken for the given doped phosphor which shows the excitation peak at 395 nm and 466 nm respectively. Emission peak observed at 593 nm and 613 nm for excitation wavelength 395 nm and same emission peak observed for excitation wavelength 466 nm comparatively less intense than 395 nm. The phase of the synthesized phosphor confirmed by X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), Photoluminescence (Pl) property shows that the given matrix is the one of the potential material which can be used for solid state lightening.

High-color-quality blue-light-pumped full-spectrum white-light-emitting diodes realized by efficient green-emitting CaY2HfScAl3O12:Ce3+ phosphors

Rare-earth doped inorganic phosphors are critical for solid-state white lighting. Particularly, efficient broadband, blue-light-excitable, green-emitting phosphors are highly needed for fabricating full-spectrum white-light-emitting diodes (WLEDs) with high-color-quality. Herein, we describe a new efficient blue-light-excited CaY2HfScAl3O12:Ce3+ green phosphor with high quantum efficiency (QE) and broad emission bandwidth. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer, excitation and emission spectra, CIE color coordinates, QE values, and temperature-dependent emission spectra have been used to characterize the samples. Rietveld refinement reveals that the CaY2HfScAl3O12 garnet compound has a cubic structure with lattice parameters of a = b = c = 12.38(13) Å, α = β = γ = 90°, and V = 1897.85(6) Å3. Impressively, the Ce3+ ions in the CaY2HfScAl3O12 host exhibit broadband excitation bands in the 300–500 nm spectral range with a maximum at 450 nm. Upon 450 nm excitation, the optimal phosphor doped with 2 mol% Ce3+ shows a broad green emission band in the wavelength range of 460–750 nm peaking around 532 nm, along with full width at half maximum of 121 nm as well as high internal QE of 78.9% and external QE of 46.6%. Ce3+ concentration-dependent luminescence properties and thermal stability at elevated temperature have been comprehensively studied. Finally, a WLED device is fabricated by utilizing CaY2HfScAl3O12:Ce3+ green phosphor, CaAlSiN3:Eu2+ red phosphor and a 450 nm blue LED chip, which generates bright full-spectrum warm-white light with ultrahigh color rendering index (Ra = 98.0, R9 = 97.5) and low correlated color temperature of 3602 K under 180 mA drive current. This work provides new insights into designing and developing efficient green phosphors for full-spectrum LED lighting.

Structural and luminescent performance and optical thermometry of Pr3+ doped SrWO4 down-conversion phosphors

A series of Pr3+ doped SrWO4 phosphors were synthesized using solid-state reaction routes. The phase composition, photoluminescence and temperature sensitivities of as-prepared materials were investigated. Rietveld refinement of measured XRD data was applied to analyze the lattice parameters. The optical transition was elaborated using UV–visible diffuse reflectance spectra and photoluminescence spectra. The photoluminescence measurements confirmed the strong visible light emission from the developed phosphors under both UV excitation at 250 nm and blue excitation at 450 nm. Notably, the maximum emission intensity was observed at a Pr3+ doping concentration of 2 mol%. Furthermore, the fluorescence intensity ratio (FIR) technique was employed, focusing on the emissions originating from the 3P0 and 1D2 state of Pr3+ within the temperature range of 298–598 K. Two FIR groups were adopted in this case, which can verify each other to achieve self-calibration. Typically, SrWO4:0.02Pr3+ exhibited remarkable performance as a temperature sensor, displaying an absolute sensitivity (Sa) of 3.11%K−1 and a relative sensitivity (Sr) of 0.81%K−1. As a result, the significant temperature-dependent PL and remarkable down-conversion luminescence make the SrWO4:Pr3+ material a promising candidate for optical thermometers and UV to visible converters of solar cell applications.

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.