Dy Phosphor Research Articles

Mixed influence of copper and some f-block elements on thermoluminescence intensity of CaSO4: Dy, P phosphors

Very little data on copper co-doped CaSO4: Dy and CaSO4: Dy, P phosphors seems to have been reported so far. In the present study the influence of copper and rare earths co-doping on thermoluminescence intensity of CaSO4: Dy, P phosphor has been investigated. Acid evaporation re-crystallization method was adopted for the synthesis purpose. Phosphors were characterized by scanning electron microscopy (SEM), photoluminescence (PL) and thermoluminescence (TL) techniques. Results obtained through this study are of mixed nature. In some cases, TL intensity is either greater or nearly equal to standard CaSO4: Dy while in other cases it is half or rather weak in comparison to standard CaSO4: Dy phosphor. Copper was found to suppress temperature peak structure above 300 o C. SEM micrographs of CaSO4: P, Dy, Cu, RE phosphors show that the particle size is in the micrometer range, 1 to 5 µm approximately. The systematic study carried out in this work is solely novel as no such report existed before. From this study it is clear now that by co-doping multi-impurities simultaneously to enhance TL characteristics of CaSO4: Dy phosphor is no longer useful because it proved otherwise.

Well-defined barium molybdate hierarchical architectures with different morphologies: Controllable synthesis, formation process, and luminescence properties

Uniform and well-dispersed barium molybdate (BaMoO4) hierarchical microspheres and microflowers have been successfully synthesized via a hydrothermal route by using sodium dodecyl benzenesulfonate (SDBS) as surfactant. The reaction conditions, including SDBS additive, pH value of the initial solution, as well as reaction temperature, have great effect on the size and morphology of the BaMoO4 products. The possible formation process of the BaMoO4 microspheres has been investigated by time-dependent experiments. The as-synthesized BaMoO4:Ln3+ (Ln=Eu, Tb, Dy, and Sm) phosphors show intense characteristic red, green, green–yellow, and orange–red emissions under ultraviolet light excitation, which might find potential applications in the fields of light emitting phosphors, advanced flat panel displays, and light-emitting diodes (LEDs).

Characterization and optical properties of Dy3+ doped nanocrystalline SrAl2O4: Eu2+ phosphor

Nanocrystalline SrAl2O4: Eu2+, Dy3+ phosphors are synthesized by a reliable low temperature combustion synthesis technique (CST). Multiple techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are used to examine the surface morphology and structural properties of SrAl2O4: Eu, Dy phosphors. The average crystal size calculated using XRD lies in nano-range. The optical properties are presented and discussed in terms of photoluminescence (PL), thermoluminescence (TL) and afterglow decay spectra. The as-obtained nanocrystalline SrAl2O4: Eu2+, Dy3+ phosphors show higher PL emission intensity (at 515nm). After being irradiated with ultraviolet (UV) light, the phosphor samples emit green long lasting phosphorescence (LLP) with excitation and emission peaks at 324nm and 515nm respectively. Using TL glow curves, the trap-depth value calculated for most intense sample is found to be 0.69eV. Furthermore, the decay curves contain a rapid and slow-decaying portion sustaining for longer time, suggesting potential applications in many fields.

Enhanced performance of cadmium selenide quantum dot-sensitized solar cells by incorporating long afterglow europium, dysprosium co-doped strontium aluminate phosphors

CdSe quantum dot-sensitized solar cells based on an efficient bifunctional structured layer composed of long afterglow SrAl2O4:Eu,Dy phosphors on top of a transparent layer of nanocrystalline TiO2 were fabricated and their photovoltaic performances were investigated. The results show that a high power conversion efficiency of 1.22% is achieved for the cell with SrAl2O4:Eu,Dy at one sun illumination (AM 1.5 G, 100mWcm−2), which is an increase of 48% compared to the cell without SrAl2O4:Eu,Dy (0.82%). After one sun illumination for 1min and subsequent turn off of the light source, the cell with SrAl2O4:Eu,Dy still shows an efficiency of 0.04% under dark condition due to the irradiation by the long persistent light from SrAl2O4:Eu,Dy. The present strategy should provide a possibility to fulfill the operation of solar cells even in the dark.

Synthesis, Persistent Luminescence, and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce, Nd, Dy, Ho, Er, Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight-excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange-red Sr3-xBaxSiO5:Eu(2+),Dy(3+) persistent luminescence phosphor was successfully developed by a two-step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non-equivalent trivalent rare earth co-dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu(2+) in Sr3SiO5 was significantly modified. The yellow persistent emission intensity of Eu(2+) was greatly enhanced by a factor of 4.5 in Sr3SiO5:Eu(2+),Nd(3+) compared with the previously reported Sr3SiO5:Eu(2+), Dy(3+). Furthermore, Sr ions were replaced with equivalent Ba to give Sr3-xBaxSiO5 :Eu(2+),Dy(3+) phosphor, which shows yellow-to-orange-red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu(2+) is significantly improved by a factor of 2.7 in Sr3-xBaxSiO5 :Eu(2+),Dy(3+) (x=0.2) compared with Sr3SiO5 :Eu(2+),Dy(3+). A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu(2+) in Sr3-xBaxSiO5:Eu(2+),RE(3+) (RE=rare earth) is also proposed and discussed.

Thermoluminescence in β-irradiated SrZnF4:Dy TLD phosphor

SrZnF4:Dy phosphor was prepared by the wet chemical synthesis and characterized for its X-ray diffraction, thermoluminescence (TL) and photoluminescence (PL) properties. The PL emission spectra for SrZnF4:Dy3+ phosphor at 351 nm excitation give emission at 481 nm (blue) and 575 nm (yellow). The TL properties of SrZnF4:Dy were studied using β-irradiation. The response curve of the prepared phosphor with high-dose β-ray exposure is linear as compared with well-known CaSO4:Dy phosphor. The TL glow curves of SrZnF4:Dy sample showed two well-defined peaks at 143°C (peak-1) and 231°C (peak-2) indicating that two sets of traps are being activated within the particular temperature range and the trapping parameter associated with the prominent glow peaks of SrZnF4:Dy is calculated by using Chen's method.

Bi3+ sensitized Y2WO6:Ln3+ (Ln = Dy, Eu, and Sm) phosphors for solar spectral conversion

The phosphors of Y2WO6:Bi3+, Ln3+ (Ln=Dy, Eu and Sm) were synthesized by solid-state reaction in this study. The crystal structure, photoluminescence properties and energy transfer mechanism were investigated. By introducing Bi3+ ions, the excitation band of the phosphors was broadened to be 250–380nm, which could be absorbed by the dye-sensitized solar cells (DSSCs). The overlap between excitation of W–O groups/Bi3+ and the emission of Ln3+ (Dy, Eu, and Sm) indicated that the probability of energy transfer from W–O groups and Bi3+ to Ln3+. The energy transfer efficiency from Bi3+ to Ln3+ (Ln=Dy, Eu and Sm) are calculated to be 16%, 20% and 58%. This work suggested that Y2WO6:Bi3+, Ln3+ (Ln=Dy, Eu and Sm) might be a promising ultraviolet-absorbing luminescent converter to enhance the photoelectrical conversion efficiency of dye-sensitized solar cells (DSSCs).

Glow curve analysis of β-particles irradiated Na21Mg(SO4)10Cl3:Dy phosphor

Dy doped Na21Mg(SO4)10Cl3 phosphor was prepared by modifying the solid state method and the formation of the compound was confirmed by X-ray diffraction (XRD) study. Morphology of the phosphor was analyzed by scanning electron microscopy (SEM). The thermally stimulated luminescence (TSL) studies of Dy doped Na21Mg(SO4)10Cl3 samples show the complex glow curve. Powder samples of Na21Mg(SO4)10Cl3:Dy were irradiated by 2.2MeV β-particles within dose range of 100–16,000mGy. Analysis of the thermoluminescence glow curves was carried out by Tm–Tstop and glow curve deconvolution (GCD) method. Trapping parameters (activation energy and frequency factor) for individual deconvoluted peaks were obtained by Chen's peak shape method. The comparison of trapping parameters between γ-ray irradiated and β-particles irradiated Na21Mg(SO4)10Cl3:Dy phosphor were also studied.

Luminescence behaviors of a novel white-emitting phosphor Bi4Si3O12:Dy prepared via sol–gel route

A kind of direct white light phosphor Bi4Si3O12:Dy3+ (BSO:Dy3+) was successfully prepared through a sol–gel technique and its luminescence properties were investigated. The white-light emission is assigned to a mixture of three emission peaks located at 460nm, 488nm and 575nm, respectively. The possible process of origin phosphorescence has been discussed and PL spectra under different temperature conditions have also been recorded. The chromaticity color coordinates of BSO:Dy phosphors at different temperatures were calculated. The thermoluminescence curves exhibit two peaks at 400 and 440K in the range of 300–550K, corresponding to the electron traps with depths of 1.225 and 1.527eV individually. The BSO samples co-doped with Dy and Tb were also prepared and their luminescence properties were investigated. This work provides a promising approach for the development of white light phosphors.

Photoluminescence and thermoluminescence study of KCaSO4Cl doped with Dy and Ce synthesized by acid distillation method

Photoluminescence and thermoluminescence properties of KCaSO4Cl doped with dysprosium and cerium have been studied. Dy/Ce doped KCaSO4Cl phosphors were synthesized by the acid distillation method. The samples were characterized by XRD, SEM, PL and TL for structural, morphological and luminescence studies. The SEM image analysis of KCaSO4Cl phosphor shows nearly spherical particles with diameter varying between 3–10μm. In the present host Dy3+ emission at 482 and 573nm is observed due to 4F9/2→6H15/2 and 4F9/2→6H13/2 transition, respectively, whereas the PL emission spectra of KCaSO4Cl:Ce phosphor shows two luminescence bands at 307nm and 326nm and are attributed to the allowed inter configurational transitions from the 5d-level to the 2F5/2 and 2F7/2 levels of Ce3+ ion. Effect of annealing on the structure of the glow curve is investigated for KCaSO4Cl:Dy phosphors. Thermoluminescence linearity has been studied for 0.1–9000Gy dose of gamma rays. Linear behavior over a large dose range between 0.1Gy and 170Gy was found. In addition to this trap parameters of KCaSO4Cl:Dy were studied using computerized glow curve deconvolution.

Photoluminescence and thermoluminescence properties of Dy3+/Eu2+ activated Na21Mg(SO4)10Cl3 phosphors

In the present work luminescence properties of rare earth (RE) doped Na21Mg(SO4)10Cl3 were studied. Modified solid state method was employed to synthesize the phosphors. The influence of RE (RE=Dy and Eu) doping on the luminescence properties of as prepared phosphor were investigated in detail. PL emission spectra of the Na21Mg(SO4)10Cl3:Dy phosphor exhibits the characteristic emission of Dy. The characteristic Dy3+ emission in the form of peaks around 482 and 576nm corresponding to transitions 4F9/2→6H15/2 and 4F9/2→6H13/2 was seen when excited by excitation wavelength 351nm. However, interesting thermoluminescence results are observed in case of Dy as well as Eu doped Na21Mg(SO4)10Cl3. The TL glow curves for Na21Mg(SO4)10Cl3:Dy exhibit broad peak composed of three overlapping peaks, these peaks were deconvoluted using deconvolution program. The peaks at different temperatures indicate that different sets of traps are being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). The peaks observed were due to formation of trap levels by γ-rays irradiation and subsequently activation of traps on thermal stimulation. The trapping parameters for both the samples were calculated using Chen's peak shape method and reported in this paper.

Impulsive excitation of mechanoluminescence in SrAl2O4:Eu, Dy phosphors prepared by solid state reaction technique in reduction atmosphere

The present paper reports the impulsive excitation of mechanoluminescence (ML) in SrAl2O4:Eu, Dy phosphor prepared by solid state reaction technique in a reduced atmosphere of 95% Ar+5% H2. The phosphors prepared exhibit such as intense ML that it can be seen in day light with naked eye. When a sample consisting of compact mass of the phosphor is deformed impulsively by the impact of a moving piston, then initially the mechanoluminescence intensity increases linearly with time, attains a peak value Im at a particular time tm, and later on it decreases with time, initially at a fast rate and then at a slow rate. The peak ML intensity Im and total ML intensity IT increase quardratically with the applied pressure and impact velocity. The ML spectra of SrAl2O4:Eu, Dy are found to be similar to the photoluminescence spectra. This result indicates that the ML is emitted from the Eu2+ ions as photoluminescence does. The ML intensity decreases with successive impact of the load onto the phosphors, whereby the diminished ML intensity can be recovered approximately by UV-irradiation. retain-->In the impulsive excitation, the complete recovery of ML intensity does not take place because the probability of radiative transition of luminescence centres formed near the newly created surfaces may decrease due the formation of surface traps. The values of tm, fast decay time and slow decay time do not change significantly with the impact velocity vo. The piezoelectrically-induced detrapping model is able to explain the characteristics of ML. According to this model, the local piezoelectric field near the activators causes the detrapping of electrons trapped in the negative oxygen vacancy and subsequently the detrapped electrons moving in the conduction band are captured by the Eu3+ ion, whereby the excited Eu2+ ions are produced and the subsequent de-excitation of excited Eu2+ ions gives rise to the light emission. It seems that, in addition to the change in crystal structure, in UV-irradiated SrAl2O4:Eu, Dy crystals, some localized electric dipoles present in the vicinity of Eu2+ ions may also enhance the piezoelectric constants of the crystals. The day light visible mechanoluminescence in SrAl2O4:Eu, Dy phosphors may be used for designing the impact stress and impact velocity sensors. Furthermore, the present investigation may be useful for determining the rise time of unknown pressure pulses and for determining the lifetime of charge carriers in shallow traps. The intense ML pulses may also be used in some specific photocatalytic reaction. The present study may also be helpful in preparing the ML-based light source by increasing the trap-depth of shallow traps. If the ML emission in certain materials will be in the ultraviolet range, then the ML pulses of short duration may be used to excite the phosphorescence and determining the decay time.

Effect of γ-radiation on NaZnSO4Cl:Ce, Dy or Mn ions and retrapping of charges in TL

The thermoluminescence (TL) characteristics and effect of γ-radiation on newly invented NaZnSO4Cl:Ce, Dy or Mn ions and retrapping of charges in TL material prepared by wet chemical method are studied. The sensitivity of the NaZnSO4Cl:Ce, Dy or Mn phosphors is higher than that of CaSO4:Dy with the broadness of the glow peak for various concentrations of Ce, Dy, Mn and different γ-rays doses. The phosphor NaZnSO4Cl:Ce has remarkable high sensitivity as compared to NaZnSO4Cl:Dy or Mn. The phosphors NaZnSO4Cl:Ce, and Mn have a simple TL glow curve structure with a single prominent peak at around the temperature 170 and 190°C, whereas NaZnSO4Cl:Dy has two peaks located at 175 and 298°C indicating single and double trapping sites respectively. TL response, fading and reusability characteristics and the trapping parameters of the phosphor are also studied and it is found that the phosphor is quite suitable for use in dosimetry of ionizing radiations.

PL and TL study of NaMgSO4F:X (X=Dy or Ce) fluoride phosphor by SSD method

Dy3+ and Ce3+ emission in NaMg(SO4)F phosphor prepared by the solid state diffusion (SSD) method is reported in this paper. The synthesized phosphors are studied for their photoluminescence (PL) and thermoluminescence (TL) characteristics. The emission spectra of Dy3+ show dominant peaks at 473nm and 572nm for an excitation of 274nm due to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions respectively, while the emission spectra of Ce3+ peak at 345nm for an excitation of 254nm due to the 5d→4f transition of Ce3+. In this host very low concentration of cerium is used. In NaMg(SO4)F:Dy3+ a single peak is observed at the temperature of 170°C and in NaMg(SO4)F:Ce it is located at 172°C when they are exposed to γ-rays for 5Gy at the rate of 0.995kGyh−1. NaMg(SO4)F:Dy is more sensitive whereas, NaMg(SO4)F:Ce less sensitive as compared to standard CaSO4:Dy. NaMg(SO4)F:Dy phosphor may be useful for TLD application.

Synthesis and characterization of needle-like BaAl2O4:Eu,Dy phosphor via

A needle-like Eu2+ and Dy3+ co-doped BaAl2O4 long-lasting phosphor was synthesized via a hydrothermal-homogeneous precipitation method assisted by cetyl trimethyl ammonium bromide (CTAB) as a template. The crystal structure, morphology and optical properties of the composites were characterized. XRD results showed that the single-phase BaAl2O4 was formed at 900 °C in an active carbon atmosphere, which was much lower than that prepared by traditional solid-state reaction method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation revealed that the precursor had well-dispersed distribution and showed needle-like morphology with the average diameter of about 100 nm and the length up to 1 μm. The final product, BaAl2O4:Eu2+,Dy3+ phosphor, inherited the needle-like shape from precursor via adding the surfactant CTAB. After irradiation by ultraviolet radiation with 355 nm for 5 min, the phosphors emitted bluish green color long-lasting phosphorescence corresponding to the typical emission of Eu2+ ion. Both the photoluminescence spectra and luminance decay revealed that the phosphor had efficient luminescent and long-lasting properties.

Impulsive Excitation Of Mechanoluminescence In γ-ray Irradiated ZnAl2O4:Dy Phosphors synthesized By Solution Combustion Technique

The mechanoluminescence (ML) of γ-irradiated ZnAl2O4: Dy phosphor has been studied. ZnAl2O4 samples having different concentrations of Dy were prepared by solution combustion technique by using hydrazine as a fuel. ML was excited impulsively by dropping a load onto the sample. Two distinct peaks have been observed in the ML intensity versus time curve. Maximum intensity is obtained for 0.1 mol% of Dy doped ZnAl2O4 phosphor. ML spectra of the phosphors show two distinct peaks around 482 nm and 585 nm which is characteristic emission of Dy 3+ . It is also observed that the ML intensity of the samples increases almost linearly with increasing mass of the sample and gamma ray doses given to the sample. Experimental results suggest that the ML excitation is related to the movement of dislocation with defect centres and it may be used for dosimeter applications. Copyright © 2013 VBRI press.

Evaluation of trapping parameters in KCaSO4Cl: X (X=Ce, Dy, Mn or Pb) phosphor by TL

Polycrystalline KCaSO4Cl: (Ce, Dy, Mn and Pb) phosphors prepared by solid state diffusion method have been studied for its trapping parameters by thermoluminescence (TL) phenomenon. The TL glow curves of KCaSO4Cl: (Ce, Dy, Mn and Pb) phosphor for different concentrations have been recorded at a heating rate of 2°Csec−1 and irradiated at a dose rate of 0.995kGyh−1 for 5Gy. The TL glow curves of γ-irradiated KCaSO4Cl: (Ce, Dy, Mn and Pb) phosphors show one glow peak indicating that only one set of traps is being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). The trapping parameters associated with the prominent glow peak of KCaSO4Cl: (Ce, Dy, Mn and Pb) is calculated by using Chen's half width method. The phosphors KCaSO4Cl: Ce, and Pb show first order kinetics while, Dy and Mn show the second order kinetics. The trap depth and frequency factors have been studied subsequently. The release of hole or electron from defect centers at the characteristic trap site initiates the luminescence process in this material.

Thermoluminescence study of MnO doped borophosphate glass samples for radiation dosimetry

MnO doped calcium fluoroborophosphate glasses of the composition 20 CaF2–50 P2O5–(30−x)B2O3:x MnO in mol% with x ranging from 0.2 to 1.0 (in steps of 0.2) were synthesized. The samples were exposed to different γ-ray doses in the range 250–1000Gy and their thermoluminescence (TL) was recorded in the temperature range ambient to 300°C. The glow curves of all these samples exhibited an intense principal peak at about 200°C followed by a feeble high temperature peak at about 300°C. The TL response of integral TL output as well as TL of the principal peak exhibited perfectly linear increase with the dose within the range of 250–1000Gy. However, the gradual increase of MnO content in the glass matrix caused a decrement in the TL output. Such mechanism is explained based on different valence states of Mn ions in the glass matrix and the quenching effect is assumed to be well exploited to measure the high radiation doses required in radiation processing facilities without saturating the PMT of the reader. The comparison of TL response of the studied glasses with that of CaSO4:Dy phosphor indicated an improvement in the dose response in terms of linearity and adequate sensitivity for the measurement of high doses.

Structural and photoluminescence properties of Dy3+ co-doped and Eu2+ activated MAl2O4 (M = Ba, Ca, Sr) nanophosphors

Long afterglow alkaline earth aluminates MAl2O4:Eu, Dy (M: Ca,Sr,Ba) phosphors are generally synthesized by the solid-state process which is more feasible than other conventional processes in terms of operation and large-scale production. However, the constituents of phosphors synthesized using this process are usually not mixed well, the particles agglomerates and very high temperature requirement to synthesize the final powder make it undesirable. In order to circumvent these problems, MAl2O4:Eu, Dy (Ca,Ba,Sr) phosphors were prepared at low temperatures (500°C) by the solution–combustion of corresponding metal nitrate–urea solution mixtures, over a time of 5–10min. In order to elucidate the relationship between the constituent, structure and PL properties product’s particle size, morphological and structural properties were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), while the characteristic luminescence properties were investigated using emission spectra. The low temperature monoclinic structure for both CaAl2O4 and SrAl2O4 and the hexagonal structure of BaAl2O4 were observed. The emission spectra of these phosphors indicated that all of them are broad band, and the only emission peaks around 448, 490 and 515nm of CaAl2O4:Eu, Dy, BaAl2O4:Eu, Dy and SrAl2O4:Eu, Dy, respectively, are due to 5d→4f transition of Eu2+. The decay curves implied that these phosphors contain fast, medium and slow-decay process. The Dy3+ trap levels may be considered to be responsible for the long afterglow phosphorescence at room temperature.

Photoluminescence and thermoluminescence of Ce3+ ions doped in LiAl5O8 and NaAl11O17 aluminate systems

The aluminate phosphors LiAl5O8:Ce; NaAl11O17:Ce were synthesized by combustion synthesis. Photoluminescence (PL) and thermoluminescence (TL) characteristics of the phosphors have been reported in this paper. The Photoluminescence (PL) emission spectra of the LiAl5O8:Ce phosphors show strong Ce3+ emission at around 310nm for the excitation at wavelength of 254nm and in NaAl11O17:Ce emission is at 350nm for the excitation at 254nm wavelength of light due to the 5d→4f transition. The TL glow curves of the LiAl5O8:Ce and NaAl11O17:Ce materials show a single peak at 245°C and 255°C respectively, indicating single type of trapping sites due to γ-irradiated effect. The relative intensities of the peaks are found to increase with different (from 0.1Gy to 50Gy) γ-ray exposure. The maximum TL sensitivity for 50Gy dose of the LiAl5O8:Ce phosphor is nearly 1.38 times whereas NaAl11O17:Ce phosphor 5.69 times higher than commercially available standard CaSO4:Dy phosphor. These phosphors may be useful for TLD materials.